Possible Deviation From Specified Value During The Pressure Test (8 Of 12)

Possible Deviation from Specified Value during the Pressure Test
High pressure and lower pressure normal first, after a long period of driving, the low pressure falls below the specified value (the evaporator in the heater and A/C unit iced up).
Possible causes for the deviation from specified value and their solutions
One in or on the removed refrigerant circuit pressure/temperature sensor or temperature sensor sends incorrect values. Use the Vehicle Diagnostic Tester in the"Guided Fault Finding" function. Refer to Component Location Overview - A/C System . Activation of the A/C compressor is faulty. Use the Vehicle Diagnostic Tester in the"Guided Fault Finding" function. If one of the valves installed in the refrigerant circuit is faulty or does not work correctly. Refer to Refrigerant Circuit . One in or on the removed refrigerant circuit pressure/temperature sensor or temperature sensor sends incorrect values. Use the Vehicle Diagnostic Tester in the"Guided Fault Finding" function. Refer to Component Location Overview - A/C System . Moisture in refrigerant circuit -- Check the measured values of the different pressure/temperature sensor and temperature sensor when operating the A/C system, and replace the components with incorrect measured values. Use the Vehicle Diagnostic Tester in the"Guided Fault Finding" function. Refer to Component Location Overview - A/C System .-- Check the activation and function of the A/C compressor and service using the Vehicle Diagnostic Tester in the"Guided Fault Finding" function.-- Check the function and activation of the various valves installed in the refrigerant circuit via the pressure distribution in the refrigerant circuit. Use the Vehicle Diagnostic Tester in the"Guided Fault Finding" function. Refer to Refrigerant Circuit .-- If no malfunction can be determined, replace the desiccant bag/dryer cartridge (or reservoir/receiver/dryer) and evacuate the refrigerant circuit for at least three hours.
Final Procedures
-- Charge the refrigerant circuit. Refer to REFRIGERANT CIRCUIT, CHARGING .-- Repeat the test. Refer to ELECTRICALLY-DRIVEN A/C COMPRESSOR, CHECKING PRESSURE WITH A/C SYSTEM SWITCHED ON .

NOTE:

First, it is not necessary to clean the refrigerant circuit (flushing with refrigerant R1234yf) in case of this complaint because generally only a small amount of moisture is in the system and this can be removed by a long evacuation. Refer to REFRIGERANT CIRCUIT, CLEANING .

If a problem involving moisture in refrigerant circuit only occurs after a lengthy operating period or only infrequently (low pressure drops below specification and evaporator ices up), it is sufficient to replace the dryer installed in receiver/dryer (adjust quantity of refrigerant oil). Refrigerant circuit is then to be evacuated for at least three hours.

With this malfunction, evaporator may ice up although the quantity of refrigerant in circuit is OK.

A malfunction on the Evaporator Vent Temperature Sensor -G263- or/and on the pressure/temperature sensor the can lead to the refrigerant circuit freezing-up. For this concern also pay attention to the measured values of the different pressure/temperature sensor in the refrigerant circuit. Use the Vehicle Diagnostic Tester in the"Guided Fault Finding" function. Refer to COOLING OUTPUT, CHECKING .

Refer to Possible Deviation From Specified Value During The Pressure Test (1 Of 12) for additional information.