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Home >> Audi >> 2020 >> SQ8 Premium Plus >> Repair and Diagnosis >> External Pages >> Different car >> Section 325 (Air Conditioning (Refrigerant R1234YF Servicing) (Tools & Testing Equipment)) >> 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 (11 Of 11)

Possible Deviation from Specified Value During the Pressure Test (11 Of 11)

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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 does not increase or only increases slightly above pressure with engine stopped.
  • The low pressure does not drop or drops only slightly.
Possible causes for the deviation from specified value and their solutions
  • No activation of the A/C compressor. Use the Vehicle Diagnostic Tester in the "Guided Fault Finding" function.
  • If equipped, the Refrigerant Shut-Off Valve 1 -- is faulty (closed)
-- Check the activation and function of the A/C compressor (and the Refrigerant Shut-Off Valve 1 --, the Refrigerant Shut-Off Valve 2 --). Use the Vehicle Diagnostic Tester in the "Guided Fault Finding" function of the A/C compressor and the battery regulation. If no malfunction can be determined replace the expansion valve on the evaporator in the heater and A/C unit. Refer to Refrigerant Circuit (vehicle-specific service information).
  • Constriction or obstruction in refrigerant circuit (for example, inside the refrigerant line between the service connection "low pressure side" and the A/C compressor).
-- If there is a blockage 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 (vehicle-specific service information).-- If the hose or pipe is kinked or constricted, replace this component. Refer to Refrigerant Circuit (vehicle-specific service information).
  • A/C compressor faulty.
-- Replace the A/C compressor. Refer to COMPONENTS, REPLACING and A/C Compressor (vehicle-specific service information).
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 .
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