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.

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.