64 50... A/C efficiency test (R 134a)
Observe the following conditions prior to the A/C efficiency test:
- Provide a MoDiC or DIS. Safeguard electrical system integrity by checking the fault memory (no faults in the fault memory).
- Provide a thermometer with separate gauge.
- Perform the test in a suitable work bay with an ambient temperature between 20°C and 30°C.
Re 1:
Connect MoDiC or DIS to car and display evaporator temperature.
Re 2:
Position a thermometer with a separate gauge approx. 5 cm below the roof liner at the height of the B-pillar. Lay gauge outwards out of vehicle interior.
Re 3:
Heating up vehicle interior:
- "A/C button" is not activated during the heating process
- Close all windows and doors.
- Set recirculated air mode.
- In A/C menu (MMI) in Air distribution index tab: select 100 % footwell for driver and front passenger and 100 % defrosting for driver (this applies here to driver and front passenger)
- Maximum temperature setting (28°C)
- Maximum fan speed (adjust 9 pixels from 9 possible on front A/C control panel)
- Run engine at approx. 2000 RPM until operating temperature is reached, then idle speed.
A/C efficiency test:
Turn on A/C compressor via "A/C button" at a vehicle interior temperature of 50°C.
Vehicles with MAX-AC button ("MAX"):
- Activation of MAX-AC (= maximum chilling capacity)
Vehicles without MAX-AC button ("MAX"):
- Set maximum chilling capacity by means of following steps:
- Temperature setting = 16°C
- Fan setting 9 pixels from 9 possible
- Stratification maximum cold (4 blue bars)
Evaporator sensor temperature must be ≤ 15°C after 3-4 minutes at approx. 2000 RPM.
Draw off A/C system see 64 50 009 Drawing off, evacuating and filling A/C system (R 134a) if this temperature is not reached. Measure amount of refrigerant drawn off.
If drawn-off quantity does not correspond to specified fill quantity, see 64 50 A/C SYSTEM, REFRIGERANT AMOUNTS E71/N54, M57T2, N63 .
If fill quantity is correct, continue troubleshooting by pressure measurement.