A/C Refrigerant System Cooling Performance, Checking

A/C Refrigerant System Cooling Performance, Checking

NOTE:
- A/C evaporator temperature switch -E33- (if equipped) switches A/C compressor OFF only in special instances so evaporator does not ice up; variable displacement A/C compressor maintains temperature of 0 degrees C (32 degrees F) in evaporator.
- Cooling performance on Climatronic equipped vehicles can also be checked using VAS 5051/5052 tester in mode "Guided Fault Finding".

Test conditions
- A/C refrigerant system fully charged
- A/C clutch -N25- and compressor function OK
- Condenser and radiator clean and free of obstructions
- Air distribution can be adjusted properly
- Wiring OK as per wiring diagram
- Outside (ambient) temperature 20 degrees C-30 degrees C (68 degrees F-86 degrees F)

Checking
- Start engine.
- Set temperature control to maximum "cold" (if Manual A/C) or "LO" (if Climatronic).
- Manual A/C: press A/C button and select second blower speed.
- Climatronic: Select minimum blower speed (manual override) by pressing "decrease blower speed" button (observe front "blower speed" display in control head).
- Adjust air distribution to instrument panel outlets.
- Insert thermometer into center instrument panel outlet.
- Raise engine speed to approximately 1500 RPM.

Specified result
With normal humidity and outside (ambient) temperature between 20 degrees -25 degrees C (68 degrees -77 degrees F), system is sufficiently charged if air temperature from center instrument panel vent drops below 10 degrees C (50 degrees F) within one minute.

For higher ambient temperatures and/or higher humidity, specified air temperature from center instrument panel vent can be slightly higher.