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Home >> Audi >> 2021 >> A4 Quattro Premium Plus, 2.0L Eng VIN B >> Repair and Diagnosis (Single Page) >> Heating, Ventilation & A/C (HVAC) >> A/C Compressor >> 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 (6 Of 11)

Possible Deviation From Specified Value During The Pressure Test (6 Of 11)

Possible Deviation from Specified Value during the Pressure Test
  • The required cooling output is not attained in the heater and A/C unit evaporator (and in the evaporator for battery cooling).
  • The high pressure pipe corresponds to the specified value
  • The low pressure corresponds to the specified value or is too low
Possible causes for the deviation from specified value and their solutions
  • The activation of the A/C compressor and if equipped the refrigerant shut-off valve 1 the refrigerant shut-off valve 2 is faulty. Use the Vehicle Diagnostic Tester in the"Guided Fault Finding"  function for the A/C system and the battery regulation.
-- Check the activation and function of the A/C compressor (and if equipped the refrigerant shut-off valve 1 and the refrigerant shut-off valve 2) and if necessary service. Use the Vehicle Diagnostic Tester in the"Guided Fault Finding"  function of the A/C compressor and the battery regulation. If this is OK extract refrigerant from the refrigerant circuit.
  • There is too little refrigerant in the refrigerant circuit.
-- Extract refrigerant from the refrigerant circuit. Refer to REFRIGERANT CIRCUIT, DISCHARGING .-- If the extracted refrigerant quantity is significantly less than the specified capacity (more that 100 g (3.5 oz)). Refer to Technical Data , and look for leaks and correct. Refer to LEAKS, FINDING .-- If the extracted refrigerant quantity corresponds to the specified capacity or is only slightly smaller (less than 100 g (3.5 oz)). Refer to Technical Data and Technical Data . Check the refrigerant shut-off valve for function. Refer to the Refrigerant Circuit .
  • The expansion valve for the evaporator in the heater and A/C unit is faulty. Refer to Refrigerant Circuit .
  • A refrigerant shut-off valve is faulty (closed). Use the Vehicle Diagnostic Tester in the"Guided Fault Finding"  function for the A/C system and the battery regulation. Refer to Refrigerant Circuit .
-- If equipped check the function of the installed shut-off valve. Refer to Refrigerant Circuit .-- Replace the expansion valve for the evaporator in the heater and A/C unit. Refer to Refrigerant Circuit .
  • Too much refrigerant oil in the refrigerant circuit
-- Clean the refrigerant circuit (flush with refrigerant R1234yf). Refer to REFRIGERANT CIRCUIT, CLEANING .-- Replace the expansion valve for the evaporator in the A/C unit (and for the evaporator for battery cooling) as well as the desiccant bag/dryer cartridge (or receiver/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 .