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Home >> Audi >> 2020 >> SQ8 Premium Plus >> Repair and Diagnosis >> External Pages >> Different car >> Section 90 (Air Conditioning (Refrigerant R1234YF Tools & Testing Equipment)) >> 87 Air Conditioning >> Working With A/C Service Station >> Pressures, Checking >> Mechanically Driven A/C Compressor, Checking Pressure With A/C System Switched On >> Possible deviation from specified value during the pressure test (5 Of 9)

Possible deviation from specified value during the pressure test (5 Of 9)

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Possible deviation from specified value during the pressure test
  • The required cooling is reached next after some or a long running time the cooling output is no longer sufficient.
  • The high pressure and low pressure are normal.
  • After some time the high pressure raises above the specified value, the low pressure corresponds to the specified value or it falls under the specified value.
Possible causes for the deviation from specified value and their solutions
  • Radiator for coolant, condenser is contaminated or the activation of the radiator fan is not OK.
-- Check the activation of the radiator fan and if necessary service. Use the Vehicle Diagnostic Tester in the "Guided Fault Finding" function of the A/C system.-- Check the condenser and radiator for the condenser for contamination and if necessary clean. Refer to Refrigerant Circuit (vehicle-specific service information) and [For engine(s) CWGD] Radiator/Radiator Fan or [For engine(s) DPVA] Radiator/Radiator Fan or [For engine(s) DMSA] Radiator/Radiator Fan .
  • The activation of the A/C Compressor Regulator Valve -N280- is faulty.
-- Check the activation of the A/C Compressor Regulator Valve A/C Compressor Regulator Valve -N280- and the measured value of the Evaporator Vent Temperature Sensor -G263- and if necessary service. Use the Vehicle Diagnostic Tester in the "Guided Fault Finding" function of the A/C system.
  • Too much refrigerant in the refrigerant circuit
-- Extract refrigerant from the refrigerant circuit. Refer to REFRIGERANT CIRCUIT, DISCHARGING .-- If the extracted refrigerant quantity is substantially greater (more than 100 g (3.5 oz)) than the specified capacity. (refer to Technical Data (vehicle-specific service information), there is too much refrigerant in the refrigerant circuit. Refill the refrigerant circuit with the correct quantity of R1234yf and repeat the test.
  • A/C Compressor Regulator Valve -N280- or A/C compressor is faulty
-- Check the function of the A/C Compressor Regulator Valve A/C Compressor Regulator Valve -N280- and if necessary remove the A/C Compressor Regulator Valve 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 and Refer to COMPONENTS, REPLACING .-- Replace the A/C Compressor Regulator Valve 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), expansion valve and desiccant bag/dryer cartridge (or replace the reservoir/receiver/dryer). Refer to COMPONENTS, REPLACING and Refrigerant Circuit (vehicle-specific service information) and Refer to REFRIGERANT CIRCUIT, CLEANING .
  • Too much refrigerant oil in the refrigerant circuit
  • Moisture in refrigerant circuit
-- Extract refrigerant from the refrigerant circuit. Refer to REFRIGERANT CIRCUIT, DISCHARGING .-- If the extracted refrigerant quantity meets the specified capacity or is only slightly smaller (maximum 100 g (3.5 oz)) (refer to Technical Data (vehicle-specific service information) there too much refrigerant oil is in the refrigerant circuit.-- Clean the refrigerant circuit (flush with refrigerant R1234yf). Refer to REFRIGERANT CIRCUIT, CLEANING .-- Replace the expansion valve and desiccant bag/dryer cartridge (or reservoir/receiver/dryer). Refer to COMPONENTS, REPLACING and Refrigerant Circuit (vehicle-specific service information).
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:

If there is too much refrigerant oil in the circuit, the A/C compressor must be emptied and the desiccant bag (the dryer cartridge) or the receiver/receiver/dryer must be replaced. After cleaning (flushing with refrigerant R1234yf) (refer to REFRIGERANT CIRCUIT, CLEANING ) fill the refrigerant circuit with the correct quantity of refrigerant oil. Refer to APPROVED REFRIGERANT OILS AND REFRIGERANT OIL CAPACITIES (vehicle-specific service information) and Refrigerant Circuit (vehicle-specific service information).

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- can also cause icing-up of refrigerant circuit. For this concern also pay attention to the measured value of the Evaporator Vent Temperature Sensor Evaporator Vent Temperature Sensor -G263-. Use the Vehicle Diagnostic Tester in the "Guided Fault Finding" function of the A/C system and refer to Component Location Overview - A/C System (vehicle-specific service information).

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