Performance Test (R 134A) - Refrigerant System

Mechanical compressor
Mechanical compressors have a constant power rating and are controlled by switching a magnetic coupling on and off. the following conditions must be fulfilled for this test.
1. MoDic or BMW Service Tester
2. thermometer
3. Compressor load (intake air temperature of approx. 50 °C)

Ref. Point 1:
Connect MoDic or BMW Service Tester to the vehicle and display the evaporator temperature.

Ref. Point 2:
Fit a thermometer approx. 5 cm under the vehicle headliner at the top of the B pillar and attach the display unit to the outside face.

Ref. Point 3:
Set heater to maximum setting. Switch on and set air-conditioning system to circulated air mode. Set car blower to speed 4 or maximum speed. Shut all windows and doors. Start up vehicle and run engine at approx. 2000 rpm.

Heat up interior of vehicle until the compressor stops cutting out. When the system is intact, this is reached at approx. 50 °C. The temperature difference between interior and evaporator must be at least 40 °C.

If this temperature differential is not achieved, drain the system and measure the volume of refrigerant drained. If this drawn off volume is approximately equal to the nominal fill quantity, refer to troubleshooting by means of pressure measurement.

Performance-controlled compressor
The performance-controlled compressor is only switched on once at low load. This has the advantage of stopping unpleasant engagement impacts since the compressor starts up very easily. the performance of the compressor i.e. the displacement volume, is controlled by the low pressure side.

This means that a shortage of refrigerant of up to approx. half the nominal fill quantity is scarcely noticeable. For this reason, a slight lack of refrigerant cannot be detected using the air conditioner test described above. Perform troubleshooting by means of pressure measurement, refer to troubleshooting by means of pressure measurement.