Electrically-Driven A/C Compressor, Checking Pressure With A/C System Switched On
Special Tools And Workshop Equipment Required
- Battery Charger :VAS5904
Pressures, Checking. Refer to PRESSURES, CHECKING .
Refrigerant Circuit Pressures Specified Values, Vehicles without Heat Pump. Refer to PRESSURES, CHECKING .
Refrigerant Circuit Pressures Specified Values, Vehicles with Heat Pump. Refer to PRESSURES, CHECKING .
Pressures, Checking
Working on the refrigerant circuit with the A/C Service Station (check the pressure here) usually requires, although not necessary, the high-voltage system to be disabled.
-- Charge the vehicle battery, for example, using the Battery Charger :VAS5904 in the battery support mode to minimize the number of automatic starts during the test- and measuring procedures when the ready mode is active. Refer to BATTERY, CHARGING and HIGH VOLTAGE SYSTEM GENERAL WARNINGS .
-- For testing and measurement procedures that require the ready mode to be active or the ignition to be switched on, the selector lever must be in the "P" position and the parking brake must be activated. The required tools must be placed so that they do not come into contact with any rotating components in the engine and they must also not go into the vicinity of the rotating components when the engine is running.
Also move the selector lever into position "P" and activate the parking brake for testing and measuring procedures which require the ignition to be on, but do not require the ready mode to be active.
The ready mode is displayed in the Instrument Cluster Control Module -J285- above the "power meter". Refer to service/repair/system information.
For activating and deactivating the ready mode. Refer to the service/repair/system information (while doing so, note the display in the Instrument Cluster Control Module -J285-).
-- On vehicles with a high-voltage system, switch off (deactivate) the "auxiliary climate control" function. Refer to the service/repair/system information and Infotainment/MMI service/repair/system information.
-- Switch off the ignition.
-- Connect the A/C Service Station. Refer to A/C SERVICE STATION ON REFRIGERANT CIRCUIT, CONNECTING .
Is a concern occurs on only on evaporator, on vehicles with two evaporators (a evaporator in the heater and A/C unit and an evaporator on the high-voltage battery heat exchanger) check the pressure in the refrigerant circuit, is this okay? Check the line connection between the evaporator in question and the exit of line connection at distribution point of refrigerant lines (for constriction). If no malfunction can be detected, discharge the refrigerant circuit and charge it with the specified refrigerant quantity. Then check the pressure and the A/C system cooling output again, if the concern is present again check/replace the following components: If the concern only occurs on the evaporator in the heater and A/C unit, check the shut-off valve in from of the evaporator in the heater and A/C unit (it is not open in the activated state and lets the refrigerant flow through). Replace the expansion valve on the evaporator in the heater and A/C unit id no malfunction can be determined on the shut-off valve. If there is a concern only on the evaporator on the high-voltage battery heat exchanger, check the activation of the shut-off valve on the expansion valve on the evaporator and high-voltage battery heat exchanger (it is not closed in the activated state and does not let refrigerant flow through). Refer to REFRIGERANT CIRCUIT or REFRIGERANT CIRCUIT .
Test Requirements
- The A/C Service Station in connected to the refrigerant circuit. Refer to A/C SERVICE STATION ON REFRIGERANT CIRCUIT, CONNECTING .
- Pay attention to the test requirements for checking the pressures in the refrigerant circuit with the ignition switched off. Refer to.
- The pressures in the refrigerant circuit with the ignition turned off meet the specifications. Refer to.
- Pay attention to the test requirements for checking the cooling output. Refer to REPAIR INFORMATION .
The switching pressures for the activation of the Electrical A/C Compressor -V470- and the Radiator Fan -V7- are vehicle-specific. Use the Vehicle Diagnostic Tester in the "Guided Fault Finding" function for the A/C system and the battery regulation.
Pressures must be measured at the service connections; the component location for these connections are vehicle-specific. Refer to REFRIGERANT CIRCUIT or REFRIGERANT CIRCUIT .
- The engine is warm (at an ambient temperature below 25 °C (77 °F)).
If the engine is not warm perform a road test.
For the cooling output test the engine must be warm but at an ambient temperature smaller than 25 °C (77 °F) a specific A/C system cooling output it is necessary that the engine and lower ambient temperatures are warm.
- Charge the vehicle battery, for example, using the Battery Charger :VAS5904 in the battery support mode to minimize the number of automatic starts during the test- and measuring procedures when the ready mode is active. Refer to BATTERY, CHARGING and HIGH VOLTAGE SYSTEM GENERAL WARNINGS .
-- Activate the ready mode (the engine must run). Refer to the appropriate service/repair/system information.
-- Adjust the A/C system to maximum cooling output. Refer to REPAIR INFORMATION .
- The Electrical A/C Compressor -V470- is activated and runs. Use the Vehicle Diagnostic Tester in the "Guided Fault Finding" function for the A/C system and the battery regulation. Refer to REFRIGERANT CIRCUIT or REFRIGERANT CIRCUIT .
The activation of the electrically driven A/C compressor occurs from the vehicle electrical system. The engine speed does not have any effect on the A/C cooling output.
The A/C compressor is currently not actuated at the maximum specified speed (of approximately 8500/min) on a stationary or slow moving vehicle (up to a speed of approximately 45 km/h (28 mph)) (the A/C compressor speed is limited to approximately 5000/min).
The activation of the electrically driven A/C compressor can be monitored by the Guided Fault Finding using the Vehicle Diagnostic Tester in the "Guided Fault Finding" Function for A/C System and the Battery Regulation.
All of the test requirements marked with a * are vehicle-specific and described in the repair information for the vehicle. Refer to REPAIR INFORMATION .
If the A/C compressor is not activated while ready mode is active:
-- Determine and eliminate cause for example by checking air conditioner DTC memory. Use the Vehicle Diagnostic Tester in the "Guided Fault Finding" function of the A/C system and the battery regulation.
- The radiator and condenser are clean (if necessary clean)*. Refer to REFRIGERANT CIRCUIT or REFRIGERANT CIRCUIT and RADIATOR/RADIATOR FAN (CZCA, CZDA, CZTA) , RADIATOR/COOLANT FAN (CBPA, CKJA) , RADIATOR/RADIATOR FAN (CNLA, CRJA) , RADIATOR/RADIATOR FAN (CVCA, CUUA, CUUB, DELA, DEBA, DEJA, DGMA) and RADIATOR/RADIATOR FAN (CPLA, CPPA, CPKA, CPRA) .
- The heat shield insulation on the expansion valve is OK and installed correctly*. Refer to REFRIGERANT CIRCUIT or REFRIGERANT CIRCUIT .
- All air guides, covers and seals are OK and correctly installed*. Refer to COMPONENT LOCATION OVERVIEW - A/C SYSTEM .
- The diagnostic of the A/C system does not determine a malfunction (with the ready mode active and the A/C system switched on) in the measured value block no compressor shut-off condition is shown. Using the Vehicle Diagnostic Tester in the "Guided Fault Finding" function for the A/C system and the battery regulation.
- The various pressure/temperature sensors installed on or in the refrigerant circuit provide valid measured values when the A/C system is being used. To check, use the Vehicle Diagnostic Tester in the "Guided Fault Finding" function. Refer to REFRIGERANT CIRCUIT . If no errors can be detected, evacuate the refrigerant.
- The airflow through the dust and pollen filter is not impaired by debris*. Refer to COMPONENT LOCATION OVERVIEW - A/C SYSTEM .
- The heater and A/C unit does not draw in any secondary air at the highest fresh air blower speed. Evaporator and heater not drawing in secondary air at maximum fresh-air blower speed. *Refer to REPAIR INFORMATION .
- The air doors in the heater and A/C unit, in the heater and in the evaporator reach their end position*. Refer to REPAIR INFORMATION .
- Fresh-air intake ducts beneath hood and in passenger compartment as well as corresponding water drain valves OK*. Refer to COMPONENT LOCATION OVERVIEW - A/C SYSTEM .
- Vehicle is not exposed to direct sunlight. Refer to REPAIR INFORMATION .
- The ambient temperature is greater than 15 °C (59 °F).
- All instrument panel vents are open *.
Adjustment for example on the Front A/C Display Control Head -E87- (and the Rear A/C Display Control Head -E265- on vehicles with two heater and A/C units) *. Refer to REPAIR INFORMATION and REFRIGERANT CIRCUIT .
Adjustment for example on the Front A/C Display Control Head -E87- *:
-- Preselect "Auto" mode (A/C compressor on).
-- Set temperature pre-selector switch to "cold" or "LO" for driver's side and front passenger's side (and left and right rear seats in vehicles with two heater and A/C units)*.
Adjustment on the A/C Control Module -J301- *:
-- Press A/C button and Rec- or recirculated air button*.
-- Turn rotary temperature control towards "cold" stop*.
-- Position the fresh-air blower dial in the position "4" (maximum fresh air blower speed)*.
The following system test conditions should be met:
- The Radiator Fan -V7- is operated or the Radiator Fan -V7- and Radiator Fan 2 -V177- runs (minimum in 1 step).* Refer to REPAIR INFORMATION and RADIATOR/RADIATOR FAN (CZCA, CZDA, CZTA) , RADIATOR/COOLANT FAN (CBPA, CKJA) , RADIATOR/RADIATOR FAN (CNLA, CRJA) , RADIATOR/RADIATOR FAN (CVCA, CUUA, CUUB, DELA, DEBA, DEJA, DGMA) and RADIATOR/RADIATOR FAN (CPLA, CPPA, CPKA, CPRA) .
On specific versions the fan is switched on after the refrigerant circuit pressure specified value is exceeded. Use the Vehicle Diagnostic Tester in the "Guided Fault Finding" function of the A/C system and the battery regulation.
- Fresh Air Blower -V2- (and Rear Fresh Air Blower -V80- in vehicles with two heater and A/C units) running at maximum speed.*
- Recirculated/fresh-air door set to "Recirculated air mode" (within one minute, after starting vehicle, air-flow door is closed and recirculated-air door is opened)*
- The coolant shut-off valve is closed.* Refer to REPAIR INFORMATION and COMPONENT LOCATION OVERVIEW - A/C SYSTEM ..
- The pump/valve unit valves are closed and there is no coolant circulation pump delivery.* Refer to REPAIR INFORMATION and REFRIGERANT CIRCUIT
The activation of the electrically-driven A/C compressor takes place from the vehicle electrical system, the engine speed does not have an influence on the A/C system cooling output. Use the Vehicle Diagnostic Tester in the "Guided Fault Finding" function of the A/C system and the battery regulation.
The A/C compressor is currently not actuated at the maximum specified speed (of approximately 8500/min) on a stationary or slow moving vehicle (up to a speed of approximately 45 km/h (28 mph)) (the A/C compressor speed is limited to approximately 5000/min).
The activation of the electrically driven A/C compressor can be monitored by the Guided Fault Finding using the Vehicle Diagnostic Tester in the "Guided Fault Finding" Function for A/C System and the Battery Regulation.
Pressures must be measured at the service connections; the component location for these connections are vehicle-specific. Refer to REFRIGERANT CIRCUIT or REFRIGERANT CIRCUIT .
Specified Values for the Refrigerant Circuit Pressures
- Refrigerant Circuit Pressures Specified Values, Vehicles without Heat Pump. Refer to PRESSURES, CHECKING .
- Refrigerant Circuit Pressures Specified Values, Vehicles with Heat Pump. Refer to PRESSURES, CHECKING .
The specified and current speed for the activation of the Electrical A/C Compressor -V470- and the Radiator Fan -V7- are vehicle-specific. Use the Vehicle Diagnostic Tester in the "Guided Fault Finding" function for the A/C system and the battery regulation.
Pressures must be measured at the service connections; the component location for these connections are vehicle-specific. Refer to REFRIGERANT CIRCUIT or REFRIGERANT CIRCUIT .
Refrigerant Circuit Pressures Specified Values, Vehicles Without Heat Pump
- Observe the test requirements. Refer to PRESSURES, CHECKING .
-- Pay attention to the pressure indicator (for example the pressure gauge) of the A/C Service Station.
The switching pressures for the activation of the Electrical A/C Compressor -V470- and the Radiator Fan -V7- /Radiator Fan 2 -V177- are vehicle-specific. Use the Vehicle Diagnostic Tester in the "Guided Fault Finding" function for the A/C system and the battery regulation.
Pressures must be measured at the service connections; the component location for these connections are vehicle-specific. Refer to REFRIGERANT CIRCUIT or REFRIGERANT CIRCUIT
High-Pressure Side:
From the output pressure (when connecting the pressure gauge) raises up to maximum 20 bar (290 psi) pressure (depending on the ambient temperature and the operating conditions of the A/C system).
Low-Pressure Side:
Decreasing from initial pressure (when connecting the pressure gauges) to a value between 1.5 and 2.3 bar (21.8 and 33.4 psi) absolute pressure (depending on the required cooling output).
A/C Compressor Speed:
Depending on the required cooling output between 800 and 8500/min (currently a maximum of 5000/min for parked vehicles).
The temperature of the air downstream from evaporator, the current A/C compressor speed and the pressure of the refrigerant on the high pressure side depending on the vehicle are displayed by the different control modules (for example by the Front A/C Display Control Head -E87-, the Climatronic Control Module -J255-, the Thermal Management Control Module -J1024- or the A/C Control Module -J301-). Use the Vehicle Diagnostic Tester in the "Guided Fault Finding" function of the A/C system and the battery regulation.
If a high cooling output is required (for example, a high outside temperature and the blower speed set on high), then the A/C compressor will not bring the pressure on the low pressure side to the required value (for example, for a certain time after turning on the A/C). The A/C compressor is not actuated at the maximum specified speed (of approximately 8500/min) on a stationary or slow moving vehicle (up to a speed of approximately 45 km/h (28 mph)) (the A/C compressor speed is limited to approximately 5000/min). After a vehicle reaches a speed of more than approximately 45 km/h (28 mph), the limit for the maximum permissible A/C compressor speed is lifted. At a A/C compressor speed of 5000/min, a high outside temperature and a high fresh air blower speed (inefficient environmental controls), the A/C compressor output (the delivery volume) is no longer sufficient to reduce the pressure on the low pressure side to the target value. To check the A/C compressor control under these conditions, for example, the fresh air blower is activated only with approximately 40% of the maximum voltage, check the pressures at a lower fresh air blower speed. Use the Vehicle Diagnostic Tester in the "Guided Fault Finding" function for A/C system and the battery regulation. Refer to REPAIR INFORMATION .
If there is a low cooling output (for example an exterior temperature of 20 °C (68 °F) and a low fresh air blower speed) the pressure on the high pressure side increases only to a value of 6 to 7 bar (87 to 102 psi) (the absence of energy is low, the refrigerant is quickly cooled in the condenser). To check the A/C compressor control and the pressure in the refrigerant circuit under these conditions for example the activating the fresh air blower with maximum voltage, adjusting the A/C system to maximum heat output and recirculating air mode. Use the Vehicle Diagnostic Tester in the "Guided Fault Finding" function of the A/C system. Refer to REPAIR INFORMATION .
Under unfavorable conditions (very high ambient temperatures, high humidity), pressure on high-pressure side may increase to max. 29 bar (420 psi).
The specified speed of the A/C compressor depending on the vehicle is displayed from different control modules (for example by the Front A/C Display Control Head -E87-, Climatronic Control Module -J255- or the A/C Control Module -J301-). Use the Vehicle Diagnostic Tester in the "Guided Fault Finding" function of the A/C system.
The measured high pressure from different sensors (for example from the High Pressure Sensor -G65-, from the Refrigerant Circuit Pressure Sensor -G805- or the A/C Pressure/Temperature Sensor -G395-) is displayed by the vehicle (for example from the Front A/C Display Control Head -E87-, the A/C Control Module -J301-, the Thermal Management Control Module -J1024- or the Climatronic Control Module -J255-). Use the Vehicle Diagnostic Tester in the "Guided Fault Finding" function of the A/C system.
Depending on the A/C compressor speed and the control characteristic of the expansion valve, the low pressure settles within the A/C compressor output range in the tolerance range (1.5 to 2.3 bar (21.8 to 33.4 psi) positive pressure).
The specified speed of the A/C compressor must for this test be greater than 1500 RPM. Use the Vehicle Diagnostic Tester in the "Guided Fault Finding" function of the A/C compressor.
In setting "maximum cooling output" the target speed of the A/C compressor is regulated to approximately 4000 up to 5000/min. This value is vehicle-specific and is displayed as the measured value from the corresponding control module (for example from the display control head, the Front A/C Display Control Head -E87-, Climatronic Control Module -J255- or the Thermal Management Control Module -J1024-). Use the Vehicle Diagnostic Tester in the "Guided Fault Finding" function for the A/C system and the battery regulation.
At absolute pressure, 0 bar (0 psi) corresponds to absolute vacuum. Normal ambient pressure corresponds to 1 bar (14.5 psi) absolute pressure. On the scales of most pressure gauges, 0 bar (0 psi) corresponds to an absolute pressure of 1 bar (14.5 psi) (can be seen from -1 bar (-14.5 psi) mark below 0). Use the Vehicle Diagnostic Tester in the "Guided Fault Finding" function for the A/C System.
If, for a vehicle with two evaporators (one in the heater and A/C unit and one for battery cooling), the measured temperature on one of the evaporators corresponds to the specified value or the specified value falls short, but does not reach the required specified value on the other evaporator, the following adjustment is performed: the corresponding control module (for example battery regulation control module or the thermal management control module) activates the electric A/C compressor with increased speed (thereby increasing the A/C system cooling output and decreasing the pressure on the low pressure side as well as the evaporator temperature) via additional control modules (for example the electric drive power and control electronics and the A/C compressor control module). If on the evaporator the specified value for the temperature falls short, the corresponding control module (for example the battery regulation control module) activates the shut-off valve (for example the refrigerant shut-off valve 1 or the refrigerant shut-off valve 2) so that no more refrigerant flows through the evaporator which is too cold. Use the Vehicle Diagnostic Tester in the "Guided Fault Finding" function of the A/C system and the battery regulation. Refer to REPAIR INFORMATION . and COMPONENT LOCATION OVERVIEW - A/C SYSTEM .
Because the output of the evaporator in the battery cooling module is noticeably smaller than the output of the evaporator in the heater and A/C unit, because of too little refrigerant in the circuit the required specified temperature in the battery cooling module may be reached but the specified temperature in the heater and A/C unit is no longer reached (although the A/C compressor is activated with a higher speed). Refer to REPAIR INFORMATION . and REFRIGERANT CIRCUIT or REFRIGERANT CIRCUIT . .
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| Possible Deviation from Specified Value During the Pressure Test |
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| Possible causes for the deviation from specified value and their solutions |
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| Final Procedures |
| -- Charge the refrigerant circuit. Refer to WORKING WITH A/C SERVICE STATION .-- Repeat the test. Refer to PRESSURES, CHECKING . |
If For This Complaint A Malfunction Is Determined In The Diagnostic, Check The Refrigerant Circuit For A Constriction Or Blockage (A Constriction Or A Blockage In The Refrigerant Circuit Can Also Lead To These Complaints). If nothing is determined here, clean the refrigerant circuit (flush with refrigerant R1234yf). Refer to REFRIGERANT CIRCUIT .
Check the measured values of the sensors for Evaporator Vent Temperature Sensor -G263- and if equipped the temperature sensor before hybrid battery evaporator and the temperature sensor after hybrid battery evaporator as well at the activation of the A/C compressor via the corresponding control module. Use the Vehicle Diagnostic Tester in the "Guided Fault Finding" function for the A/C system and the battery regulation.
If there is an error in the measured value of the Evaporator Vent Temperature Sensor -G263-, the temperature sensor before hybrid battery evaporator or the temperature sensor after hybrid battery evaporator (depending on the vehicle use the Vehicle Diagnostic Tester in the "Guided Fault Finding" function for the A/C system and the battery regulation) this can lead to problems in the cooling output and the evaporator can freeze-up.
With a malfunction on one of the temperature sensors, the evaporator may ice up even though the quantity of refrigerant in the refrigerant circuit is OK.
If the A/C system function is not OK after repeating the test, for example after replacing expansion valve, clean the refrigerant circuit by flushing using the refrigerant R1234yf. Refer to REFRIGERANT CIRCUIT . Replace the A/C compressor and dryer cartridge (or reservoir/receiver/dryer). Refer to REFRIGERANT CIRCUIT or REFRIGERANT CIRCUIT .
If the expansion valve in the heater and A/C unit evaporator or the shut-off valve is faulty (permanently closed or does not open sufficiently), the A/C compressor is actuated to maximum output and the low pressure drops to specification or below (compressor draws off refrigerant from low-pressure side). Since the refrigerant cannot flow via the expansion valve, the cooling output is not attained, high pressure may also not increase or only increase slightly due to the absence of energy. Use the Vehicle Diagnostic Tester in the "Guided Fault Finding" Function for the A/C System and the Battery Regulation. Refer to REFRIGERANT CIRCUIT or REFRIGERANT CIRCUIT .
The evaporator in the heater and A/C Unit has considerably more output than the evaporator for battery cooling. The refrigerant shut-off valve 2 on the expansion valve in the battery cooling module depending on the version is activated for cooling the Electric Vehicle Battery -A2- (depending on the vehicle use the Vehicle Diagnostic Tester in the "Guided Fault Finding" function of the A/C system and the battery regulation) first after a specific battery temperature by the corresponding control module (for example from the battery regulation control module) so that the energy transformation via the evaporator for battery cooling is not or only slightly raised. Use the Vehicle Diagnostic Tester in the "Guided Fault Finding" function for the A/C system and the battery regulation. Refer to REFRIGERANT CIRCUIT or REFRIGERANT CIRCUIT .
| Possible Deviation From Specified Value During The Pressure Test |
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| Possible causes for the deviation from specified value and their solutions |
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| Final Procedures |
| -- Charge the refrigerant circuit. Refer to WORKING WITH A/C SERVICE STATION .-- Repeat the test. Refer to PRESSURES, CHECKING . |
If too much refrigerant oil is located in the circuit, the A/C compressor must be discharges and replace the receiver/receiver/dryer (or dryer cartridge). Refer to REFRIGERANT CIRCUIT or REFRIGERANT CIRCUIT . After cleaning the refrigerant circuit (flushing with refrigerant R1234yf. Refer to REFRIGERANT CIRCUIT ) fill it with the correct quantity of refrigerant oil in the refrigerant circuit. Refer to REPAIR INFORMATION .
Check the measured values of the Evaporator Vent Temperature Sensor -G263- and the activation of the A/C compressor. If the measured value of the Evaporator Vent Temperature Sensor -G263- or the activation of the A/C compressor is faulty, the evaporator can freeze-up or the cooling output is not reached. Use the Vehicle Diagnostic Tester in the "Guided Fault Finding" function for the A/C system and the battery regulation. Refer to COMPONENT LOCATION OVERVIEW - A/C SYSTEM . and A/C COMPRESSOR .
With this malfunction, evaporator may ice up although the quantity of refrigerant in circuit is OK.
Likewise, the refrigerant circuit may become iced if there is a malfunction on the Evaporator Vent Temperature Sensor -G263- or/and on the temperature sensor after hybrid battery evaporator. For this concern also pay attention to the measured value of the Evaporator Vent Temperature Sensor -G263- and the temperature sensor after hybrid battery evaporator (on vehicles with battery cooling module). Use the Vehicle Diagnostic Tester in the "Guided Fault Finding" function of the A/C system and the battery regulation. Refer to COMPONENT LOCATION OVERVIEW - A/C SYSTEM . .
| Possible Deviation From Specified Value During The Pressure Test |
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| Possible causes for the deviation from specified value and their solutions |
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| Final Procedures |
| -- Charge the refrigerant circuit. Refer to WORKING WITH A/C SERVICE STATION .-- Repeat the test. Refer to PRESSURES, CHECKING . |
For the malfunction "high pressure normal, low pressure too low" With this malfunction, evaporator may ice up, although quantity of refrigerant in circuit is OK.
If there is a malfunction an the refrigerant circuit, it was not activated and operates nevertheless, it is not necessary to clean the refrigerant circuit (flush with refrigerant R1234yf). Refer to REFRIGERANT CIRCUIT . For this error it is sufficient to replace the A/C compressor (pay attention to the refrigerant oil quantity in the A/C compressor). Refer to REFRIGERANT CIRCUIT and A/C COMPRESSOR .
If there is a fault in the A/C compressor (the A/C compressor is activated by the A/C compressor control module at too high of a speed), it is not necessary to clean the refrigerant circuit (flushing with refrigerant R1234yf. Refer to REFRIGERANT CIRCUIT ). For this malfunction it is sufficient to replace the A/C compressor (pay attention to the refrigerant oil quantity in the A/C compressor). Refer to TECHNICAL DATA and REFRIGERANT CIRCUIT or REFRIGERANT CIRCUIT .
If the expansion valve (or one of the two expansion valves) is faulty (permanently closed or does not open sufficiently), the A/C compressor is also actuated to maximum output and the pressure on the low pressure side drops to specified value or below (compressor draws off refrigerant from the low-pressure side). Since the refrigerant cannot flow via the faulty expansion valve, the cooling output in the downstream evaporator is not attained and the high pressure may also not increase or only increase slightly due to the absence of energy. The A/C compressor may thereby be activated with a higher speed since the required cooling output is not attained in an evaporator. The same applies if the function or the activation of the refrigerant shut-off valve 1 or the refrigerant shut-off valve 2 is faulty. Use the Vehicle Diagnostic Tester in the "Guided Fault Finding" function for the A/C system and the battery regulation. Refer to REFRIGERANT CIRCUIT or REFRIGERANT CIRCUIT .
Check the measured values for the Evaporator Vent Temperature Sensor -G263- (and the measured values for the temperature sensor before hybrid battery evaporator and the temperature sensor after hybrid battery evaporator) as well as the activation of the A/C compressor by the A/C compressor control module. If the measured value of the Evaporator Vent Temperature Sensor -G263- (the temperature sensor before hybrid battery evaporator, the temperature sensor after hybrid battery evaporator) or the activation of the A/C compressor is faulty, the evaporator can freeze-up or the required cooling output is not read. Use the Vehicle Diagnostic Tester in the "Guided Fault Finding" function for the A/C system and the battery regulation. Refer to COMPONENT LOCATION OVERVIEW - A/C SYSTEM .
| Possible Deviation From Specified Value During The Pressure Test |
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| Possible causes for the deviation from specified value and their solutions |
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| Final Procedures |
| -- Charge the refrigerant circuit. Refer to WORKING WITH A/C SERVICE STATION .-- Repeat the test. Refer to PRESSURES, CHECKING . |
This fault may also be caused by too much refrigerant oil in the refrigerant circuit. Overfilling with refrigerant oil can occur if, for example, the compressor has been replaced without adjusting the quantity of refrigerant oil. Refer to REFRIGERANT CIRCUIT and TECHNICAL DATA . fIf there is too much refrigerant oil in the refrigerant circuit, clean the refrigerant circuit (flush with refrigerant R1234yf). Refer to REFRIGERANT CIRCUIT .
If the expansion valve for the heater and A/C unit evaporator (or for the evaporator in the battery cooling) is faulty (permanently closed or does not open sufficiently), the A/C compressor is actuated to maximum output and the low pressure drops to the target value or below (compressor draws off refrigerant from low-pressure side). Since the refrigerant cannot flow via the expansion valve, the cooling output is not attained and the high pressure may also not increase or only increase slightly due to the absence of energy. The same applies if the function or the activation of the refrigerant shut-off valve 1 or the refrigerant shut-off valve 2 is faulty. Use the Vehicle Diagnostic Tester in the "Guided Fault Finding" function for the A/C system and the battery regulation. Refer to REFRIGERANT CIRCUIT or REFRIGERANT CIRCUIT .
| Possible Deviation From Specified Value During The Pressure Test |
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| Possible causes for the deviation from specified value and their solutions |
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| Final Procedures |
| -- Charge the refrigerant circuit. Refer to WORKING WITH A/C SERVICE STATION .-- Repeat the test. Refer to PRESSURES, CHECKING . |
This Fault May Also Be Caused By Too Much Refrigerant Oil In The Refrigerant Circuit. Overfilling With Refrigerant Oil Can Occur If, For Example, The Compressor Has Been Replaced Without Adjusting The Quantity Of Refrigerant Oil. Refer to REFRIGERANT CIRCUIT and TECHNICAL DATA . If there is too much refrigerant oil in the refrigerant circuit, clean the refrigerant circuit (flush with refrigerant R1234yf). Refer to REFRIGERANT CIRCUIT .
If the expansion valve for the heater and A/C unit evaporator (or for the evaporator in the battery cooling) is faulty (permanently closed or does not open sufficiently), the A/C compressor is actuated to maximum output and the low pressure drops to the target value or below (compressor draws off refrigerant from low-pressure side). Since the refrigerant cannot flow via the expansion valve, the cooling output is not attained and the high pressure may also not increase or only increase slightly due to the absence of energy. The same applies if the function or the activation of the refrigerant shut-off valve 1 or the refrigerant shut-off valve 2 is faulty. Use the Vehicle Diagnostic Tester in the "Guided Fault Finding" function for the A/C system and the battery regulation. Refer to REFRIGERANT CIRCUIT or REFRIGERANT CIRCUIT
| Possible Deviation From Specified Value During The Pressure Test |
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| Possible causes for the deviation from specified value and their solutions |
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| Final Procedures |
| -- Charge the refrigerant circuit. Refer to WORKING WITH A/C SERVICE STATION .-- Repeat the test. Refer to PRESSURES, CHECKING . |
Pay attention to the notes to do so. Refer to PRESSURES, CHECKING and PRESSURES, CHECKING .
| Possible Deviation From Specified Value During The Pressure Test |
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| Possible causes for the deviation from specified value and their solutions |
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| Final Procedures |
| -- Charge the refrigerant circuit. Refer to WORKING WITH A/C SERVICE STATION .-- Repeat the test. Refer to PRESSURES, CHECKING . |
Pay attention to the notes to do so. Refer to PRESSURES, CHECKING and PRESSURES, CHECKING .
| Possible Deviation From Specified Value During The Pressure Test |
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| Possible causes for the deviation from specified value and their solutions |
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| Final Procedures |
| -- Charge the refrigerant circuit. Refer to WORKING WITH A/C SERVICE STATION .-- Repeat the test. Refer to PRESSURES, CHECKING . |
Read the supporting information. Refer to PRESSURES, CHECKING .
| Possible Deviation From Specified Value During The Pressure Test |
|---|
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| Possible causes for the deviation from specified value and their solutions |
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| Final Procedures |
| -- Charge the refrigerant circuit. Refer to WORKING WITH A/C SERVICE STATION .-- Repeat the test. Refer to PRESSURES, CHECKING . |
If the A/C system function when repeating the test is not OK, replace the expansion valve and desiccant bag/dryer cartridge (or receiver/receiver/dryer) and if equipped refrigerant shut-off valve. Refer to REFRIGERANT CIRCUIT or REFRIGERANT CIRCUIT .
With this malfunction, evaporator may ice up although the quantity of refrigerant in circuit is OK.
If the expansion valve in the heater and A/C unit evaporator or the refrigerant shut-off valve 1 is malfunctioning (permanently closed or does not open sufficiently), the A/C compressor is actuated to maximum output and the low pressure drops to specification or below (compressor draws off refrigerant from low-pressure side). As the refrigerant cannot flow via the expansion valve (the refrigerant shut-off valve), if the cooling output is not attained, high pressure may also not increase or only increase slightly due to the absence of energy. Use the Vehicle Diagnostic Tester in the "Guided Fault Finding" function for the A/C system and the battery regulation. Refer to REFRIGERANT CIRCUIT or REFRIGERANT CIRCUIT .
If the expansion valve on the evaporator for the battery cooling is faulty (or if the functionality or activation of the refrigerant shut-off valve 2 is malfunctioning), constantly closed or does not open enough, then the A/C compressor is likewise activated with the maximum output (the required temperatures in the battery cooling module are not attained). The pressure on the low pressure side only falls to the specified value or lower when there is no cooling output requested at the same time in the heater and A/C unit (the refrigerant shut-off valve 1 is activated and is closed). The A/C compressor extracts the refrigerant from the low pressure side from both evaporators). Since, however, no refrigerant can flow over the expansion valve in the A/C unit (the refrigerant shut-off valve 1) and the cooling output for the battery cooling is not attained (there is a malfunction in the area of the battery cooling), the electrical A/C compressor will be activated with a higher speed. Since, however, no refrigerant can flow through, the pressure on the low pressure side falls below the specified value. In addition, the high pressure may never or only slightly increase, due to the absence of energy. Use the Vehicle Diagnostic Tester in the "Guided Fault Finding" function for the A/C system and the battery regulation. Refer to REFRIGERANT CIRCUIT or REFRIGERANT CIRCUIT .
Since the evaporator output for the battery cooling is noticeably smaller than the evaporator output in the A/C unit, the required specified temperature may still be reached for the battery cooling with too little refrigerant in the circuit, but the specified temperature in the heater and A/C unit evaporator will no longer be attainable (even though the A/C compressor is activated with an increased speed).
If there is too much refrigerant oil in the circuit, the A/C compressor must be emptied and the desiccant bag (the dryer cartridge) or the receiver/receiver/dryer must be replaced. After cleaning (flushing with refrigerant R1234yf) fill the refrigerant circuit with the correct quantity of refrigerant oil. Refer to REFRIGERANT CIRCUIT , TECHNICAL DATA . and REFRIGERANT CIRCUIT or REFRIGERANT CIRCUIT .
Refer to PRESSURES, CHECKING for further information.
| Possible Deviation From Specified Value During The Pressure Test |
|---|
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| Possible causes for the deviation from specified value and their solutions |
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| Final Procedures |
| -- Charge the refrigerant circuit. Refer to WORKING WITH A/C SERVICE STATION .-- Repeat the test. Refer to PRESSURES, CHECKING . |
For cooling the Electric Vehicle Battery -A2- (hybrid battery) the refrigerant shut-off valve 1 is currently activated from a specific battery temperature for example from the battery regulation control module. If the A/C system driver is not already activated at this time, the Electrical A/C Compressor -V470- is activated via the A/C Compressor Control Module -J842- for example by the battery regulation control module. The temperature of the air (or the coolant) before and after the evaporator for battery cooling module is calculated by the respective control module (for example by the battery regulation control module). If at the same time it is determined that the cooling is not sufficient this is stored for example in the battery regulation control module. Use the Vehicle Diagnostic Tester in the "Guided Fault Finding" function of the A/C system and the battery regulation.
The temperature of the air (or the coolant) and the evaporator cooling output in the battery cooling module is determined via the installed temperature sensor (it currently cannot be measured using a thermometer while operating) and may only for this reason be checked using the Guided Fault Finding. Use the Vehicle Diagnostic Tester in the "Guided Fault Finding" function of the A/C System and the battery regulation.
Refer to PRESSURES, CHECKING for further information.
| Possible Deviation From Specified Value During The Pressure Test |
|---|
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| Possible causes for the deviation from specified value and their solutions |
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| Final Procedures |
| -- Charge the refrigerant circuit. Refer to WORKING WITH A/C SERVICE STATION .-- Repeat the test. Refer to PRESSURES, CHECKING . |
Refrigerant Circuit Pressures Specified Values, Vehicles with Heat Pump
On vehicles with a high-voltage system and heat pump installed in the refrigerant circuit and electrically activated vehicles which regulate the flow of the refrigerant in the refrigerant circuit depending on the current operating condition. There are different versions of these valves. Refer to REFRIGERANT CIRCUIT or REFRIGERANT CIRCUIT and use the Vehicle Diagnostic Tester in the "Guided Fault Finding" function.
On vehicles with the "heat pump" function and/or "high-voltage battery cooling" in not all operating conditions is the A/C system high pressure on the service connection of the high pressure side. Depending on the A/C system operating condition, the refrigerant circuit pressure on the high pressure side can only be measured via the pressure/temperature sensor installed in the refrigerant circuit on these vehicles. Refer to REFRIGERANT CIRCUIT or REFRIGERANT CIRCUIT and use the Vehicle Diagnostic Tester in the "Guided Fault Finding" function.
On these vehicles the refrigerant circuit of the A/C system is used not only to cool the vehicle interior but also to cool the hybrid battery unit (via the refrigerant circuit for the high-voltage system) and to heat the vehicle interior (at low ambient temperature) via the heat pump function. So in order for these functions to be performed, the various valves, pressure and temperature sensors as well as the pumps in the refrigerant circuit and in the high-voltage system coolant circuit must be installed correctly and function correctly. Use the Vehicle Diagnostic Tester in the "Guided Fault Finding" function. Refer to REFRIGERANT CIRCUIT , or REFRIGERANT CIRCUIT and REPAIR INFORMATION .
To determine the possible cause of a malfunction, different routines are stored in the basic setting of the thermal management control module, which activate these functions: "Cooling the A/C system", "heat pump", and "Cooling the components of the high-voltage system". Use the Vehicle Diagnostic Tester in the "Guided Fault Finding" function.
High-Pressure Side:
Increasing from initial pressure (when connecting the pressure gauges) to a maximum of 20 bar (290 psi).
Depending on the layout of the high pressure side service connection and the operating condition, the high pressure can only be measured via the pressure/temperature sensor installed in the refrigerant circuit. Refer to REFRIGERANT CIRCUIT or REFRIGERANT CIRCUIT .
Low-Pressure Side:
Decreasing from initial pressure (when connecting the pressure gauges) to a value between absolute pressure (depending on the required cooling output).
A/C Compressor Speed:
Depending on the required cooling output between 800 and 8500/min (currently a maximum of 5000/min for parked vehicles).
The temperature of the air downstream of the evaporator, the current A/C compressor speed and the pressure of the refrigerant on the high pressure side are displayed as the measured value by various control modules (for example, by the thermal management control module, the front A/C display control head or the Climatronic control module), depending on the vehicle. Refer to REFRIGERANT CIRCUIT and use the Vehicle Diagnostic Tester in the "Guided Fault Finding" function.
If a high cooling output is required (for example, a high outside temperature and the blower speed set on high), then the A/C compressor will not bring the pressure on the low pressure side to the required value (for example, for a certain time after turning on the A/C). The A/C compressor is not actuated at the maximum specified speed (of approximately 8500/min) on a stationary or slow moving vehicle (up to a speed of approximately 45 km/h (28 mph)) (the A/C compressor speed is limited to approximately 5000/min). After a vehicle reaches a speed of more than approximately 45 km/h (28 mph), the limit for the maximum permissible A/C compressor speed is lifted. At a A/C compressor speed of 5000/min, a high outside temperature and a high fresh air blower speed (inefficient environmental controls), the A/C compressor output (the delivery volume) is no longer sufficient to reduce the pressure on the low pressure side to the target value. To check the A/C compressor control under these conditions, for example, the fresh air blower is activated only with approximately 40% of the maximum voltage, check the pressures at a lower fresh air blower speed. Use the Vehicle Diagnostic Tester in the "Guided Fault Finding" function (for A/C system and the battery regulation). Refer to REPAIR INFORMATION .
Under unfavorable conditions (very high ambient temperatures, high humidity), pressure on high-pressure side may increase to max. 29 bar (421 psi).
The specified speed of the A/C compressor is displayed and the measured value for example from the thermal management control module using the Vehicle Diagnostic Tester in the "Guided Fault Finding" function.
The refrigerant circuit pressure (low or high pressure) measured by the different pressure/temperature sensors depending on the respective operating condition is displayed as the measured value by the respective control module. Use the Vehicle Diagnostic Tester in the "Guided Fault Finding" function. Refer to REFRIGERANT CIRCUIT or REFRIGERANT CIRCUIT .
The low pressure settles depending on the A/C compressor speed and the control characteristic of the expansion valve (on the evaporator of the front heater and A/C unit) within the compressor output range in tolerance range (1.5 to 2.3 bar (21.8 to 33.4 psi) positive pressure).
The target speed for the A/C compressor must be greater than 1500/min for this test.
In setting "maximum cooling output" the target speed is regulated to approximately 4000 up to 5000/min. This value is vehicle-specific and is displayed and the measured value of the respective control module using the Vehicle Diagnostic Tester in the "Guided Fault Finding" function.
At absolute pressure, 0 bar (0 psi) corresponds to absolute vacuum. Normal ambient pressure corresponds to 1 bar (14.5 psi) absolute pressure. 0 bar (0 psi) pressure corresponds to an absolute pressure of 1 bar (14.5 psi) on most pressure gauges (indicated by -1 bar (-14.5 psi) below 0).
If on a vehicle with two evaporators (one in the heater and A/C unit and one for cooling the heater and A/C unit for example the heat exchanger for the high-voltage battery) and two condensers (one in the front end for the A/C system and one as the heat exchanger for the heat pump function) depending on the selected function on a component the measured temperature or pressure, the specified value corresponds to another component whose specifications are not achieved, check the activation of the electrically activated valves installed in the refrigerant circuit. At the same time, also pay attention to the pressure distribution in the refrigerant circuit depending on the installed check valves. Use the Vehicle Diagnostic Tester in the "Guided Fault Finding" function. Refer to REFRIGERANT CIRCUIT or REFRIGERANT CIRCUIT .
For the correct A/C function it is also necessary that depending on the selected functions of the respective heater cores enough heat is supplied or removed. Therefore also pay attention to the incorporation of the heater core into the respective coolant circuit for the engine and high-voltage system and the function of the pumps and valves installed in it. Use the Vehicle Diagnostic Tester in the "Guided Fault Finding" function. Refer to COOLANT PIPES, REMOVING AND INSTALLING .
Since the evaporator for cooling the high-voltage components output (in the battery cooling module and in the high-voltage battery heat exchanger) is smaller than the evaporator output in the heater and A/C unit, the required target temperature may still be reached in the evaporator for cooling the high-voltage battery with too little refrigerant in the refrigerant circuit, but the target temperature in the heater and A/C unit evaporator will no longer be attainable (even though the A/C compressor is activated with increased A/C unit speed).
| Possible Deviation From Specified Value, The Cause And Its Elimination | |
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| Possible Deviation from Specified Value During the Pressure Test |
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| Possible causes for the deviation from specified value and their solutions |
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| Final Procedures |
| -- Charge the refrigerant circuit. Refer to WORKING WITH A/C SERVICE STATION .-- Repeat the test. Refer to PRESSURES, CHECKING . |
To Determine The Possible Cause Of A Malfunction, Different Routines Are Stored In The Basic Setting Of The Control Module (For Example In The Thermal Management Control Module) Which Activate These Functions: "Cooling The A/C System", "Heat Pump", And "Cooling The Components Of The High-Voltage System". Use The Vehicle Diagnostic Tester In The "Guided Fault Finding" Function. Refer to REFRIGERANT CIRCUIT or REFRIGERANT CIRCUIT .
If for this concern no malfunction can be determined, check the activation of the electrically activated valves installed in the refrigerant circuit next. If no error can be detected here, remove and check the check valves installed in the refrigerant circuit, if no error can be detected here clean the refrigerant circuit (flush with refrigerant R1234yf). One of these malfunctions may arise due to a constriction or a blockage in the refrigerant circuit. Refer to REFRIGERANT CIRCUIT or REFRIGERANT CIRCUIT .
On vehicles with the "heat pump" function and/or "high-voltage battery cooling" in not all operating conditions is the A/C system high pressure on the service connection of the high pressure side. Depending on the A/C system operating condition, the refrigerant circuit pressure on the high pressure side can only be measured via the pressure/temperature sensor installed in the refrigerant circuit on these vehicles. Refer to REFRIGERANT CIRCUIT or REFRIGERANT CIRCUIT and use the Vehicle Diagnostic Tester in the "Guided Fault Finding" function.
Before beginning the repair work check the measured values of the different pressure/temperature sensors installed in the refrigerant circuit. If there is an error in the measured value of a pressure/temperature sensor, this can lead to problems in the cooling output, or the evaporator in the front heater and A/C unit can ice over. Use the Vehicle Diagnostic Tester in the "Guided Fault Finding" function. Refer to REFRIGERANT CIRCUIT or REFRIGERANT CIRCUIT , and Refer to the Appropriate Wiring Diagram.
When checking the different functions (heat pump or cooling the high-voltage battery), also pay attention to the activation and function of the coolant circuit components that are involved with these functions. Refer to COOLANT PIPES, REMOVING AND INSTALLING .
If the A/C system function is not OK after repeating the test, for example after replacing expansion valve (reinstalling the old expansion valve), clean the refrigerant circuit by flushing using the refrigerant R134a. Refer to REFRIGERANT CIRCUIT . Then replace the A/C compressor and receiver/dryer or dryer cartridge.
With a malfunction on one of the temperature sensors, the evaporator may ice up even though the quantity of refrigerant in the circuit is OK.
If the expansion valve on the evaporator in the A/C unit is faulty (constantly closed or does not open far enough), the A/C compressor is activated to maximum output and the low pressure drops to the value in the graph or below (A/C compressor draws off the refrigerant from the low pressure side). Since the refrigerant cannot flow via the expansion valve, the cooling output is not attained, high pressure may also not increase or only increase slightly due to the absence of energy. Use the Vehicle Diagnostic Tester in the "Guided Fault Finding" function. Refer to REPAIR INFORMATION .
The evaporator in the heater and A/C unit has a larger output than the evaporator for cooling the high-voltage battery. Depending on the version to cool the electric vehicle battery/hybrid battery unit (hybrid battery), the expansion valve in front of this evaporator (the heat exchanger for cooling the high-voltage system components) is currently activated only from or up to a certain battery temperature by the respective control module, so that the exchange of energy via this evaporator does not increase, or only slightly. Use the Vehicle Diagnostic Tester in the "Guided Fault Finding" function. Refer to REPAIR INFORMATION . .
If there is too much refrigerant oil in the circuit, the compressor must be drained (flushed) and the receiver/dryer/dryer cartridge must be replaced. After cleaning the refrigerant circuit (flushing with refrigerant R134a. Refer to REFRIGERANT CIRCUIT ) fill it with the correct quantity of refrigerant oil in the circuit (in the A/C compressor). Refer to TECHNICAL DATA .
| Possible Deviation from Specified Value During the Pressure Test |
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| Possible causes for the deviation from specified value and their solutions |
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| Final Procedures |
| -- Charge the refrigerant circuit. Refer to WORKING WITH A/C SERVICE STATION .-- Repeat the test. Refer to PRESSURES, CHECKING . |
Read the supporting information. Refer to PRESSURES, CHECKING .
| Possible Deviation from Specified Value During the Pressure Test |
|---|
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| Possible causes for the deviation from specified value and their solutions |
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| Final Procedures |
| -- Charge the refrigerant circuit. Refer to WORKING WITH A/C SERVICE STATION .-- Repeat the test. Refer to PRESSURES, CHECKING . |
Read the supporting information. Refer to PRESSURES, CHECKING .
| Possible Deviation from Specified Value During the Pressure Test |
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| Possible causes for the deviation from specified value and their solutions |
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| Final Procedures |
| -- Charge the refrigerant circuit. Refer to WORKING WITH A/C SERVICE STATION .-- Repeat the test. Refer to PRESSURES, CHECKING . |
Read the supporting information. Refer to PRESSURES, CHECKING .
| Possible Deviation from Specified Value During the Pressure Test |
|---|
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| Possible causes for the deviation from specified value and their solutions |
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| Final Procedures |
| -- Charge the refrigerant circuit. Refer to WORKING WITH A/C SERVICE STATION .-- Repeat the test. Refer to PRESSURES, CHECKING . |
Read the supporting information. Refer to PRESSURES, CHECKING .
| Possible Deviation from Specified Value During the Pressure Test |
|---|
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| Possible causes for the deviation from specified value and their solutions |
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| Final Procedures |
| -- Charge the refrigerant circuit. Refer to WORKING WITH A/C SERVICE STATION .-- Repeat the test. Refer to PRESSURES, CHECKING . |
With this malfunction, evaporator may ice up although the quantity of refrigerant in circuit is OK.
If the expansion valve in the heater and A/C unit evaporator or the installed shut-off valve is malfunctioning (permanently closed or does not open sufficiently), the A/C compressor is actuated to maximum output and the low pressure drops to specification or below (compressor draws off refrigerant from low-pressure side). Since no (or little) the refrigerant can flow via the expansion valve, the cooling output is not attained, high pressure may also not increase or only increase slightly due to the absence of energy. Use the Vehicle Diagnostic Tester in the "Guided Fault Finding" function. Refer to REPAIR INFORMATION .
If the expansion valve for the evaporator for cooling the high-voltage components is faulty (or the function and activation is faulty) is always closed or does not open wide enough the A/C compressor is also activated with the maximum output (the required temperatures in the heat exchanger are not reached). The pressure on the low pressure side only then falls to the specified value or lower when at the same time the front heater and A/C unit no cooling output is needed. The A/C compressor extracts the refrigerant from the low pressure side from both evaporators. Because no refrigerant can low over the expansion valve in the front heater and A/C unit and the cooling output in the evaporator for cooling the high voltage battery is not reached (there is a malfunction in the area of the evaporator for the cooling of the high voltage battery) the electric A/C compressor is activated with a higher speed. If not refrigerant can flow the pressure on the low pressure side falls under the specified value, high pressure may also not increase or only increase slightly due to the absence of energy. The same applies if a valve in the refrigerant circuit is not OK a malfunction in the incorporation of the evaporator for cooling the high-voltage battery in the high-voltage system refrigerant circuit or the pump or a valve installed there is not OK. Then the High-Voltage Battery Heat Exchanger is cooled, but the cooled coolant reached the high-voltage battery heat exchanger which should not be cooled. Use the Vehicle Diagnostic Tester in the "Guided Fault Finding" function. Refer to COOLANT PIPES, REMOVING AND INSTALLING . .
Refer to PRESSURES, CHECKING for additional information.
| Possible Deviation from Specified Value During the Pressure Test |
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| Possible causes for the deviation from specified value and their solutions |
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| Final Procedures |
| -- Charge the refrigerant circuit. Refer to WORKING WITH A/C SERVICE STATION .-- Repeat the test. Refer to PRESSURES, CHECKING . |
Read the supporting information. Refer to PRESSURES, CHECKING .
| Possible Deviation from Specified Value During the Pressure Test |
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| Possible causes for the deviation from specified value and their solutions |
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| Final Procedures |
| -- Charge the refrigerant circuit. Refer to WORKING WITH A/C SERVICE STATION .-- Repeat the test. Refer to PRESSURES, CHECKING . |
First, it is not necessary to clean the refrigerant circuit (flushing with refrigerant R1234yf. Refer to REFRIGERANT CIRCUIT ) in case of this complaint because generally only a small amount of moisture is in the system and this can be removed by a long evacuation.
If a problem involving moisture in refrigerant circuit only occurs after a lengthy operating period or only infrequently (low pressure drops below specification and evaporator ices up), it is sufficient to replace the dryer installed in receiver/dryer (adjust quantity of refrigerant oil). Refrigerant circuit is then to be evacuated for at least three hours.
With this malfunction, evaporator may ice up although the quantity of refrigerant in circuit is OK.
A malfunction on the Evaporator Vent Temperature Sensor -G263- or/and on the pressure/temperature sensor the can lead to the refrigerant circuit freezing-up. For this concern also pay attention to the measured values of the different pressure/temperature sensor in the refrigerant circuit. Use the Vehicle Diagnostic Tester in the "Guided Fault Finding" function. Refer to REPAIR INFORMATION .
Refer to PRESSURES, CHECKING for additional information.
| Possible Deviation From Specified Value During The Pressure Test |
|---|
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| Possible causes for the deviation from specified value and their solutions |
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| Final Procedures |
| -- Charge the refrigerant circuit. Refer to WORKING WITH A/C SERVICE STATION .-- Repeat the test. Refer to PRESSURES, CHECKING . |
For the malfunction "high pressure normal, low pressure too low", note the following: With this fault, it may be that the evaporator in the heater and A/C unit is icing up although the refrigerant quantity in the circuit is OK.
If there is a fault in the A/C compressor (the A/C compressor is activated by the A/C compressor control module at too high of a speed), it is not necessary to clean the refrigerant circuit by flushing with refrigerant R1234yf. Refer to REFRIGERANT CIRCUIT . In this case, it is sufficient to replace the A/C compressor (observe quantity of refrigerant oil in A/C compressor and if necessary adjust).
If the expansion valve for the evaporator for cooling the high-voltage components is faulty (or the function and activation is faulty) is always closed or does not open wide enough the A/C compressor is also activated with the maximum output (the required temperatures in the heat exchanger are not reached). The pressure on the low pressure side only then falls to the specified value or lower when at the same time the front heater and A/C unit no cooling output is needed. The A/C compressor extracts the refrigerant from the low pressure side from both evaporators. Because no refrigerant can low over the expansion valve in the front heater and A/C unit and the cooling output in the evaporator for cooling the high voltage battery is not reached (there is a malfunction in the area of the evaporator for the cooling of the high voltage battery) the electric A/C compressor is activated with a higher speed. If not refrigerant can flow the pressure on the low pressure side falls under the specified value, high pressure may also not increase or only increase slightly due to the absence of energy. The same applies if a valve in the refrigerant circuit is not OK a malfunction in the incorporation of the evaporator for cooling the high-voltage battery in the high-voltage system refrigerant circuit or the pump or a valve installed there is not OK. Then the High-Voltage Battery Heat Exchanger is cooled, but the cooled coolant reached the high-voltage battery heat exchanger which should not be cooled. Use the Vehicle Diagnostic Tester in the "Guided Fault Finding" function. Refer to COOLANT PIPES, REMOVING AND INSTALLING .
A malfunction on the Evaporator Vent Temperature Sensor -G263- or/and on the pressure/temperature sensor the can lead to this concern. Also pay attention to the measured values of the different pressure/temperature sensor in the refrigerant circuit. Use the Vehicle Diagnostic Tester in the "Guided Fault Finding" function. Refer to REPAIR INFORMATION .
Refer to PRESSURES, CHECKING for additional information.
| Possible Deviation From Specified Value During The Pressure Test |
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| Possible causes for the deviation from specified value and their solutions |
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| Final Procedures |
| -- Charge the refrigerant circuit. Refer to WORKING WITH A/C SERVICE STATION .-- Repeat the test. Refer to PRESSURES, CHECKING . |
This fault may also be caused by too much refrigerant oil in the circuit. Overfilling with refrigerant oil can occur if, for example, the compressor has been replaced without adjusting the quantity of refrigerant oil.
Refer to PRESSURES, CHECKING for additional information.
| Possible Deviation from Specified Value During the Pressure Test |
|---|
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| Possible causes for the deviation from specified value and their solutions |
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| Final Procedures |
| -- Charge the refrigerant circuit. Refer to WORKING WITH A/C SERVICE STATION .-- Repeat the test. Refer to PRESSURES, CHECKING . |
Overfilling with refrigerant oil can occur if, for example, the compressor has been replaced without adjusting the quantity of refrigerant oil.
If for example the expansion valve for the evaporator in the heater and A/C unit or for the evaporator for cooling the high-voltage battery is faulty (always open) the evaporator temperature (in the heater and A/C unit) is no longer regulated that only refrigerant in gaseous state exits from the evaporator. Under certain usage conditions, liquid droplets may then be drawn in by the compressor and cause noise (liquid cannot be compressed).
If there is too much refrigerant oil in the circuit, the compressor must be drained and the receiver/dryer must be replaced. After cleaning the refrigerant circuit (flushing with refrigerant R1234yf. Refer to REFRIGERANT CIRCUIT ) fill it with the correct quantity of refrigerant oil in the circuit. Refer to TECHNICAL DATA .
Refer to PRESSURES, CHECKING for additional information.
| Possible Deviation from Specified Value During the Pressure Test |
|---|
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| Possible causes for the deviation from specified value and their solutions |
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| Final Procedures |
| -- Charge the refrigerant circuit. Refer to WORKING WITH A/C SERVICE STATION .-- Repeat the test. Refer to PRESSURES, CHECKING . |
If the required cooling output on the evaporator in the front heater and A/C unit (and on the evaporator for cooling the high-voltage battery is OK) and there is a concern due to insufficient heating performance on the heat exchanger for the heat pump operation. The cause may be in the high-voltage system coolant circuit or in the engine coolant circuit. If the pumps and valves in the high-voltage system coolant circuit is not activated correctly or its function is not OK via the evaporator (heat exchanger) for the high-voltage system components not enough heat energy is absorbed from the coolant. If the pumps and valves in the coolant circuit of the engine are not started correctly or its function are not OK via the heat exchanger for the heat pump function for absorbing the heat energy is not transferred to the coolant flowing to the heat exchanger in the heater and A/C unit. Use the Vehicle Diagnostic Tester in the "Guided Fault Finding" function. Refer to COOLANT PIPES, REMOVING AND INSTALLING .
Refer to PRESSURES, CHECKING for additional information.