Possible Deviation From Specified Value During The Pressure Test (7 Of 9)

Possible Deviation from Specified Value during the Pressure Test
The required cooling performance is obtained. The high pressure pipe corresponds to the specified value The low pressure is too low (lower than the target value)
Possible causes for the deviation from specified value and their solutions
The measured value of the Evaporator Vent Temperature Sensor -G263- is faulty. -- Check the measured value and installation of the Evaporator Vent Temperature Sensor -G263-. Use the Vehicle Diagnostic Tester in the"Guided Fault Finding" function of the A/C system. Refer to Component Location Overview - A/C System . The activation of the A/C Compressor Regulator Valve -N280- is faulty. If a shut-off valve installed in the refrigerant circuit does not open or opens incorrectly. Refer to Component Location Overview - A/C System and Refrigerant Circuit . -- Check the activation of the A/C Compressor Regulator Valve -N280- and if necessary service. Use the Vehicle Diagnostic Tester in the"Guided Fault Finding" function of the A/C system.-- If equipped check the function of the installed shut-off valves. Refer to Component Location Overview - A/C System and Refrigerant Circuit . A/C Compressor Regulator Valve -N280- or A/C compressor faulty -- Check the function of the A/C Compressor Regulator Valve -N280- and if necessary remove the A/C Compressor Regulator Valve -N280- and if necessary check for contamination. Use the Vehicle Diagnostic Tester in the"Guided Fault Finding" function of the A/C system. Refer to COMPONENTS, REPLACING .-- Replace the A/C Compressor Regulator Valve -N280- or the A/C compressor. Refer to COMPONENTS, REPLACING .-- If there is dirt in the refrigerant circuit clean the refrigerant circuit (flush with refrigerant R1234yf) and the expansion valve and desiccant bag/dryer cartridge (or replace the reservoir/receiver/dryer). Refer to REFRIGERANT CIRCUIT, CLEANING , COMPONENTS, REPLACING and Refrigerant Circuit .
Final Procedures
-- Charge the refrigerant circuit. Refer to REFRIGERANT CIRCUIT, CHARGING .-- Repeat the test. Refer to MECHANICALLY DRIVEN A/C COMPRESSOR, CHECKING PRESSURE WITH A/C SYSTEM SWITCHED ON .

NOTE:

For the malfunction "high pressure normal, low pressure too low" With this malfunction, evaporator may ice up, although quantity of refrigerant in circuit is OK.

If there is a malfunction on a present shut-off valve (the shut-off valve does not open) it is not necessary to clean the refrigerant circuit (flush with refrigerant R1234yf). Refer to REFRIGERANT CIRCUIT, CLEANING . For this malfunction it is sufficient to check the activation of the shut-off valve, if this is OK replace the shut-off valve.

If the problem is with the A/C Compressor Regulator Valve -N280- (regulating valve is not actuated but compressor operates nevertheless), refrigerant circuit needs to be cleaned (flush with refrigerant R1234yf). In this case, it is sufficient to replace the A/C compressor (observe quantity of refrigerant oil in A/C compressor). Refer to REFRIGERANT CIRCUIT, CLEANING .

If the expansion valve is faulty (constantly closed or does not open far enough), the A/C Compressor Regulator Valve -N280- is actuated to maximum output and low pressure drops to value in graph or below (the A/C compressor draws off refrigerant from low-pressure side). As however refrigerant cannot flow via the expansion valve, the cooling output is not always attained and high pressure may also not increase or only increase slightly due to the absence of energy conversion. For these malfunctions it is not necessary to clean the refrigerant circuit (flush with refrigerant R1234yf) it is sufficient to replace the expansion valve. Refer to REFRIGERANT CIRCUIT, CLEANING .

Check measured values of the Evaporator Vent Temperature Sensor -G263- and the actuation of the A/C Compressor Regulator Valve -N280-. If the measured value of the Evaporator Vent Temperature Sensor -G263- malfunctions the evaporator can ice over or the cooling output is not reached. Use the Vehicle Diagnostic Tester in the"Guided Fault Finding" function of the A/C system.