Cooling Output, Checking

Special tools and workshop equipment required

Battery Charger:VAS5904 (vehicles with high-voltage system)
Vehicle Diagnostic Tester with the "Guided Fault Finding " function and the corresponding connection lines. Refer to Workshop Equipment.
A standard thermometer (for temperature measurement; if necessary, a thermometer with two measuring probes for simultaneous measurement, for example, for temperature on the right and left).

This service information only outlines the checking procedure. Perform the detailed test for this heater function as described in the Guided Fault Finding using the Vehicle Diagnostic Tester.

Also on vehicles with a high-voltage system (Audi Q7 e-tron)

For all procedures on vehicles with a high-voltage system, pay attention to the additional warnings for these vehicles. Refer to SAFETY PRECAUTIONS .

Working near high-voltage system components is necessary for the following procedure. "Perform a visual inspection for damage to the high-voltage components and lines". Refer to SAFETY PRECAUTIONS .

Working on a high-voltage system when activated or with the ignition turned on

There is a risk of injury from the engine starting unexpectedly.

On electric and hybrid vehicles an active ready mode is difficult to identify. Parts of the body can be pinched or pulled.

-- Switch off the ignition.

-- Place the ignition key outside of the vehicle interior.

All Vehicles

The cooling output test requirements are met. Refer to A/C COOLING OUTPUT, TESTING REQUIREMENTS .

-- Close the doors, the engine hood, the windows, the sliding sunroof and the rear lid.

-- Start the engine (or activate ready mode).

-- Switch off the A/C compressor ("ECON" mode is set, the indicator lamp in the A/C and the A/C MAX buttons do not turn on).

-- Initiate the A/C system Guided Fault Finding using the Vehicle Diagnostic Tester.

-- Select the measured values for the activation of the A/C compressor and the refrigerant circuit pressure and read out the measured values in the "read measured values" function. Use the Vehicle Diagnostic Tester in the "Guided Fault Finding " function.

When testing the cooling output, it is helpful to display the following measured values of the Front A/C Display Control Head -E87- or the Display Unit -J519-. Use the Vehicle Diagnostic Tester.

The measured values of the following temperature sensors (Evaporator Vent Temperature Sensor -G263-, Left Front Upper Body Vent Temperature Sensor -G385-, Right Front Upper Body Vent Temperature Sensor -G386-, Left Footwell Vent Temperature Sensor -G261-, Right Footwell Vent Temperature Sensor -G262-).
The request or the activation of the following components (Fresh Air Blower -V2-, Rear Fresh Air Blower -V80-, Radiator Fan -V7-, Radiator Fan 2 -V177-).
The request or activation of the following components (if equipped depending on the equipment and engine type: Coolant Recirculation Pump -V50- / Thermal Management Coolant Pump 2 -V618- on vehicles with a high-voltage system / Recirculation Pump -V55-, Coolant Change-Over Valve 3 -N634- on vehicles with high-voltage system / Coolant Shut-Off Valve -N82- / Heater Coolant Shut-Off Valve -N279-).
The request or the activation of the A/C Compressor Regulator Valve -N280- (compressor switch off controls and A/C compressor actual current on vehicles without a high-voltage system).
Read the activation of the Electrical A/C Compressor -V470- (compressor switch off controls and A/C compressor speed) for vehicles with a high-voltage system.
The exterior temperature.
The measured value of the High Pressure Sensor -G65- (refrigerant pressure on vehicles without high-voltage system).

Tip:

The measured values of the High Pressure Sensor -G65-, A/C Pressure/Temperature Sensor -G395-, A/C Pressure/Temperature Sensor 2 -G826- and the activation of the Electrical A/C Compressor -V470- is done through the Thermal Management Control Module -J1024-. Therefore in Guided Fault Finding , the measured values of both control modules, Thermal Management Control Module -J1024- and the Front A/C Display Control Head -E87 - are read out alternating using the.
The High Pressure Sensor -G65- is not always present on vehicles with a high-voltage system or its measured value is not analyzed by the Thermal Management Control Module -J1024-.
During the cooling output test on vehicles with a high-voltage system, the pressure on the high pressure side is measured by the A/C Pressure/Temperature Sensor -G395- (and, if equipped, by the High Pressure Sensor -G65-), and the pressure on the low pressure side is measured by the A/C Pressure/Temperature Sensor 2 -G826- and A/C Pressure/Temperature Sensor 3 -G827-.
During the cooling output test, there is low pressure applied to the high pressure side on the service connection for vehicles with a high-voltage system. The pressure on the high pressure side can only be measured by the A/C Pressure/Temperature Sensor -G395- (and by the High Pressure Sensor -G65- only if it is equipped). Refer to SYSTEM OVERVIEW - REFRIGERANT CIRCUIT ON VEHICLES WITH HIGH-VOLTAGE SYSTEM (AUDI Q7 E-TRON) .

-- Check the refrigerant circuit pressure via the measured value of the High Pressure Sensor -G65- (Vehicles without high-voltage system).

-- The measured value of the High Pressure Sensor -G65- (if equipped), A/C Pressure/Temperature Sensor -G395-, A/C Pressure/Temperature Sensor 2 -G826- and A/C Pressure/Temperature Sensor 3 -G827- (refrigerant pressure on vehicles with a high-voltage system).

The A/C compressor is switched off. A current of 0 A (amps) for the activation of the A/C Compressor Regulator Valve -N280- is displayed (on vehicles without a high-voltage system).
The A/C compressor is switched off, A/C compressor speed is 0 RPM (on vehicles with a high-voltage system).
The refrigerant circuit pressure is same at the measured ambient temperature or is greater than the value in the table.

Ambient Temperature in °C	Displayed Pressure (Pressure in bar)
15	3.0
20	4.0
25	5.0
30	6.0
35	7.0

TIP

At absolute pressure, 0 bar corresponds to absolute vacuum. Normal ambient pressure equals approximately 1 bar absolute pressure and 0 bar pressure. On the scales of most pressure gauges, 0 bar pressure corresponds to an absolute pressure of one bar (can be seen from -1 mark below 0).
Pressure in refrigerant circuit is governed by the ambient temperature. Because heat is given off by components (for example, the radiator), the pressure displayed when the engine is warm will be slightly higher than that for the respective ambient temperature.

-- If the displayed pressure is lower than that in the table and no error is detected on the High Pressure Sensor -G65-, then there is not enough refrigerant is in the circuit.

Set the following on the Front Information Display Control Head 2 -J1060- :

Synchronize all zones by pressing the SYNC button.
Select "Auto" mode for the driver side (and the front passenger side) (the indicator lamp in the AUTO button(s) illuminate).
Temperature preset for all zones (front and rear) "cold" ("LOW" display).
The A/C compressor is on (the indicator lamp in the A/C MAX button turns on).
Preset for fresh air blower (front and rear (if equipped)) "maximum speed".
Set the airflow direction for the driver and front passenger side on the "instrument panel vent".
Set the airflow direction on the Rear A/C Display Control Head -E265- for the left and right side on the vents in the rear center console.

TIP

For the different settings. Refer to the A/C system information in the Owner's Manual.
The indicator lamp in the AUTO button turns off when performing manual changes for the airflow direction and/or the fresh air blower speed.
The maximum possible fresh air blower speed depends on various ambient influences (coolant temperature, electrical system voltage, etc.)

Vehicles without High-Voltage System

-- In the "Read measured values" function, read out the actual current, with which the A/C Compressor Regulator Valve -N280- is controlled, using the Vehicle Diagnostic Tester.

-- In the "read measured values" function, read out the refrigerant circuit pressure measured by the High Pressure Sensor -G65-. The displayed pressure goes over the value for a A/C compressor that is switched off. Use the Vehicle Diagnostic Tester.

The pressure displayed in the displayed measured value does not change and the A/C compressor activation is OK. Use the Vehicle Diagnostic Tester. Check again whether the A/C compressor is actually operating and the A/C Compressor Regulator Valve -N280- is activated. If the A/C compressor is being driven and the A/C Compressor Regulator Valve -N280- is activated, there is a malfunction in the refrigerant circuit. This may be an indication of a locking A/C Compressor Regulator Valve -N280-.
The Climatronic Control Module -J255- activates the A/C Compressor Regulator Valve -N280-, so that the air temperature reaches the specified value downstream of the evaporator (approximately 2 to 5 °C).
After starting the vehicle, a value greater than 0.55 A is displayed for the activation of the A/C Compressor Regulator Valve -N280- depending on the measured temperature, the engine speed and the electrical system voltage. As soon as the temperature measured by the Evaporator Vent Temperature Sensor -G263- approaches the specified value, activation is canceled and the compressor output is thus reduced.
Under certain operating conditions, remaining moisture in the refrigerant circuit can lead to ice build-up on the A/C Compressor Regulator Valve -N280- (and on the expansion valve). This ice build-up interferes with A/C compressor regulation. The evaporator is cooled too intensely and freezes. The freeze-up of the evaporator can be the cause for various customer complaints. Refer to LOCALIZING MALFUNCTION FOR ICE BUILD-UP ON EVAPORATOR .

-- Push the button for the recirculating air mode (the symbol for "recirculating air mode" in the recirculation button turns on).

-- Set engine speed of 2000 rpm (start of time measurement).

Vehicles with high-voltage system (Audi Q7 e-tron)

-- In the function "read measured values" of the Thermal Management Control Module -J1024- check the activation of the Electrical A/C Compressor -V470- compressor shut-off conditions and compressor speed). Use the Vehicle Diagnostic Tester.

The A/C compressor operates in the driving mode with a speed range of 700 to 8600 revolutions/minute.
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 45km/h) (the A/C compressor speed is limited to approximately 5000/min).
The A/C compressor output (the delivery volume) is not always sufficient with a A/C compressor speed of 5000/min, a very high exterior temperature (more than 35 °C) and a high fresh air blower speed (inefficient environmental controls) at lowering the air temperature to the target value downstream of the evaporator. To check the regulation of the A/C compressor under these conditions, for example, activate the fresh air blower only with approximately 40% of the maximum voltage and check the temperature at a reduced fresh air blower speed using the Vehicle Diagnostic Tester.
If little or no speed is displayed as a measured value (although the required air temperature downstream of the evaporator is not yet achieved; the speed is less than 4000 RPM), check the activation of the Electrical A/C Compressor -V470- by the A/C Compressor Control Module -J842- using the Vehicle Diagnostic Tester.

All Vehicles

-- In the "read measured values" function, read out the measured value of the Evaporator Vent Temperature Sensor -G263-. Use the Vehicle Diagnostic Tester.

-- Use a thermometer to measure the temperature of the air from the vent in the rear center console.

-- Compare the displayed value (for the Evaporator Vent Temperature Sensor -G263-) with the values in the diagram.

Fig 1: Compare Displayed Value (From Evaporator Vent Temperature Sensor) With Values In Diagram

Courtesy of AUDI OF AMERICA, LLC

A -

Air Temperature Measured by the Evaporator Vent Temperature Sensor -G263- (after Evaporator in the Front Heater and A/C Unit)

B -

Ambient Temperature

C -

Permissible Tolerance Range

Depending on the ambient temperature, the measured air temperature downstream from the front evaporator (measured value of the Evaporator Vent Temperature Sensor -G263-) must be within the specified tolerance range -C- after five minutes.
The measured temperatures from the vents of the rear center console correspond to the temperature measured by the Evaporator Vent Temperature Sensor -G263-. Permitted difference to the measured value of the Evaporator Vent Temperature Sensor -G263- + 6 °C /- 3 °C.

If the required values for the front are not reached, check the measured value of the Evaporator Vent Temperature Sensor -G263-. Compare the displayed measured value of the Evaporator Vent Temperature Sensor -G263- with the measured values of the Left Front Upper Body Vent Temperature Sensor -G385- and the Right Front Upper Body Vent Temperature Sensor -G386- with each other.
If the measured value of the Evaporator Vent Temperature Sensor -G263- is greater than the measured value of the Left Front Upper Body Vent Temperature Sensor -G385- or the Right Front Upper Body Vent Temperature Sensor -G386-, check the Evaporator Vent Temperature Sensor -G263- for proper installation. Refer to Evaporator Vent Temperature Sensor -G263-, REMOVING AND INSTALLING ) and perform an electrical test for this sensor. Use the Vehicle Diagnostic Tester.
The A/C system function can be recognized, for example, when the refrigerant line "low pressure side" (wide line in the plenum chamber between the expansion valve and the refrigerant line with the inner heat exchanger under the left fender) cools down and the refrigerant line "high pressure side" (narrow line between the inner heater core and the expansion valve) warms up.

If the measured value of the Evaporator Vent Temperature Sensor -G263- (and thus the front A/C system cooling output) is OK and if there is no complaint, the cooling output test ends.

If the measured value of the Evaporator Vent Temperature Sensor -G263- (and with it the front A/C system cooling output) is not OK, then the test requirements may not have been held. The cooling output test is performed again. Refer to COOLING OUTPUT, CHECKING . If a new cooling output test is also not OK, then check the incorporation of the heater core in the coolant circuit and check the shut-off valve function. Refer to CONNECTION DIAGRAM - COOLANT HOSES .