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Home >> Audi >> 2020 >> S4 Prestige >> Repair and Diagnosis >> External Pages >> Different car >> Section 49 (Air Conditioning (Refrigerant R1234YF Servicing) (1 Of 2)) >> 87 Air Conditioning >> Working With A/C Service Station >> Pressures, Checking >> Electrically-Driven A/C Compressor, Checking Pressure With A/C System Switched On >> Possible Deviation From Specified Value During The Pressure Test (2 Of 11)

Possible Deviation From Specified Value During The Pressure Test (2 Of 11)

WARNING: This page is about a different car, the 2021 Audi S4 and 2021 Audi A4 Quattro. However, it is still accessible from the selected car via links, so may be relevant.
Possible Deviation from Specified Value During the Pressure Test
  • The required cooling output is reached at first in the evaporator in the heater and A/C unit (and in the evaporator for battery cooling) after some time or after a longer 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 and RADIATOR/RADIATOR FAN .
  • Activation of function of the A/C compressor (or if equipped the refrigerant shut-off valve 1 or the refrigerant shut-off valve 2) is faulty.
  • Moisture in refrigerant circuit
-- Check the activation of the A/C compressor (and if equipped the refrigerant shut-off valve 1 and the refrigerant shut-off valve 2) and the measured value of the Evaporator Vent Temperature Sensor -G263-. Use the Vehicle Diagnostic Tester in the"Guided Fault Finding"  function.-- If the activation of the A/C compressor (and if equipped the refrigerant shut-off valve 1 and the refrigerant shut-off valve 2) as well as the measured value of the Evaporator Vent Temperature Sensor -G263- is OK extract the refrigerant from the refrigerant circuit. Refer to REFRIGERANT CIRCUIT, DISCHARGING .
  • Too much refrigerant in the refrigerant circuit
  • Expansion valve malfunctioning
  • If a shut-off valve installed in the refrigerant circuit does not open or opens incorrectly. Refer to Refrigerant Circuit .
  • Moisture in 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 there is too much refrigerant in the refrigerant circuit. Fill the refrigerant circuit and repeat the test. Refer to Technical Data .-- If the extracted refrigerant quantity meets the specified capacity is only slightly greater than the specified capacity (maximum 100 g (3.5 oz)) too much refrigerant oil is in the refrigerant circuit. Refer to Technical Data . Clean the refrigerant circuit (flush with refrigerant R1234yf) and fill with the correct quantity of refrigerant and refrigerant oil and repeat the test. Refer to REFRIGERANT CIRCUIT, CLEANING .-- If equipped check the function of the installed shut-off valve. Refer to Refrigerant Circuit .-- Replace the expansion valve and desiccant bag/dryer cartridge (or reservoir/receiver/dryer). Refer to COMPONENTS, REPLACING and Refrigerant Circuit .
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:

If too much refrigerant oil is located in the circuit, the A/C compressor must be discharges and replace the receiver/receiver/dryer (or dryer cartridge). Refer to Refrigerant Circuit . After cleaning the refrigerant circuit (flushing with refrigerant R1234yf) fill it with the correct quantity of refrigerant oil in the refrigerant circuit. Refer to REFRIGERANT CIRCUIT, CLEANING and Technical Data .

Check the measured values of the Evaporator Vent Temperature Sensor -G263- and the activation of the A/C compressor. If the measured value of the Evaporator Vent Temperature Sensor -G263- or the activation of the A/C compressor is faulty, the evaporator can freeze-up or the cooling output is not reached. Use the Vehicle Diagnostic Tester in the"Guided Fault Finding"  function for the A/C system and the battery regulation. Refer to Component Location Overview - A/C System and A/C Compressor .

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

Likewise, the refrigerant circuit may become iced if there is a malfunction on the Evaporator Vent Temperature Sensor -G263- or/and on the temperature sensor after hybrid battery evaporator. For this concern also pay attention to the measured value of the Evaporator Vent Temperature Sensor -G263- and the temperature sensor after hybrid battery evaporator (on vehicles with battery cooling module). Use the Vehicle Diagnostic Tester in the"Guided Fault Finding"  function of the A/C system and the battery regulation. Refer to Component Location Overview - A/C System .

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