Pressures, Checking
-- Turn off the ignition.
-- Connecting service station, refer to CONNECTING SERVICE STATION .
-- Take pressure gauge readings (two possible results).
| Ambient Temperature | Pressure in Refrigerant Circuit in Positive Pressure |
|---|---|
| 15 °C (59 °F) | 3.9 bar (56.57 psi) |
| 20 °C (68 °F) | 4.7 bar (68.17 psi) |
| 25 °C (77 °F) | 5.6 bar (81.22 psi) |
| 30 °C (86 °F) | 6.7 bar (97.18 psi) |
| 35 °C (95 °F) | 7.8 bar (113.13 psi) |
| 40 °C (104 °F) | 9.1 bar (131.98 psi) |
| 45 °C (113 °F) | 10.5 bar (152.28 psi) |
Temperature of refrigerant circuit components should be equal to ambient temperature.
Pressure will deviate from values in table if individual components of refrigerant circuit are warmer or colder.
At absolute pressure, 0 bar corresponds to absolute vacuum. Normal ambient pressure (positive pressure) corresponds to 1 bar absolute pressure. 0 pressure corresponds to an absolute pressure of one bar on most pressure gauges (indicated by 1 bar below 0).
On vehicles with High Pressure Sensor -G65- with which the measured pressure is displayed in the measured value block, the measured pressure should correspond to the values in the table.
Refer to High Pressure Sensor -G65- .
The refrigerant circuit pressure is lower than indicated in table
Not enough refrigerant in refrigerant circuit
-- Determine refrigerant circuit leaks, refer to REFRIGERANT CIRCUIT, TRACING LEAKS, WITH Electronic Leak Detector VAG 1796 .
-- Check the pressure relief valve.
If pressure relief valve has responded:
-- Check the coolant fan activation.
-- Check refrigerant lines and hoses for cross-section constrictions caused by inadequate bending radii.
-- Check refrigerant pipes and hoses for external damage.
-- If no malfunction is found, flush refrigerant circuit with compressed air and nitrogen.
The refrigerant circuit pressure is in line with table or is higher
-- Start the engine.
-- For vehicles with an electrically-driven A/C compressor, switch on the ignition.
Hybrid vehicles have a high voltage system. Danger of electrical shock! Inspect the high voltage components visually before beginning. Follow the General Warnings.
-- Set the A/C system to maximum cooling output.
If the low pressure switch was removed to connect the service station, bridge the electrical connections in the corresponding connector for the pressure measurement.
- A/C compressor is driven by the engine via A/C Clutch -N25-.
- The A/C Compressor Regulator Valve -N280- is activated by the Climatronic Control Module -J255-.
Refer to DESCRIPTION AND OPERATION .
If A/C compressor is not driven with the engine running or regulating valve is not actuated:
-- Determine and eliminate cause e.g. by checking air conditioner DTC memory.
-- Observe test conditions.
-- Check the A/C Clutch -N25- voltage supply. If it is OK, repair the A/C clutch.
-- Check activation of A/C Compressor Regulator Valve -N280-.
Refer to DESCRIPTION AND OPERATION .
- Check on vehicles with restrictor and reservoir (with internally regulated A/C compressor), refer to CHECKING WITH RESTRICTOR AND RESERVOIR, WITH INTERNALLY REGULATED A/C COMPRESSOR .
- Check on vehicles with expansion valve and receiver/dryer (with internally regulated A/C compressor), refer to CHECKING WITH EXPANSION VALVE AND RECEIVER/DRYER, WITH INTERNALLY REGULATED A/C COMPRESSOR .
- On vehicles with expansion valve and receiver/dryer (without regulated A/C compressor), refer to CHECKING WITH EXPANSION VALVE AND RECEIVER/DRYER, WITHOUT REGULATED A/C COMPRESSOR .
- Checking pressures for vehicles with restrictor, reservoir and A/C Compressor Regulator Valve -N280- (externally regulated A/C compressor), refer to CHECKING WITH RESTRICTOR, RESERVOIR AND A/C Compressor Regulator Valve -N280-, EXTERNALLY REGULATED A/C COMPRESSOR .