64 50 ... A/C Efficiency Test (R 134a)

64 50 ... A/C Efficiency Test (R 134a)


Observe the following conditions prior to the A/C efficiency test:
1. Provide a MoDiC or DIS. Safeguard electrical system integrity by checking the fault memory (no faults in the fault memory).
2. Provide a thermometer with separate gauge.
3. 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.

Air-conditioning efficiency measurement:

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 temperature sensor must be ≤15 °C after 3-4 minutes at approx. 2000 rpm engine speed.

Draw off A/C system if this temperature is not reached. Measure amount of refrigerant drawn off.

If drawn-off quantity does not correspond to specified fill quantity: supplement refrigerant and repeat test.

If fill quantity is correct, continue troubleshooting by pressure measurement.