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Home >> Audi >> 2022 >> SQ8 Premium Plus >> Repair and Diagnosis >> External Pages >> Different car >> Section 327 (Air Conditioning (Refrigerant R1234YF Servicing) (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 >> Pressures, Checking

Pressures, Checking

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Refrigerant circuit with expansion valve, receiver/dryer with or without A/C Clutch -N25- and A/C Compressor Regulator Valve -N280- (with an A/C compressor regulated from the outside)

NOTE:

Connect the A/C Service Station. Refer to A/C SERVICE STATION ON REFRIGERANT CIRCUIT, CONNECTING .

If a malfunction occurs at only one evaporator in vehicles with two evaporators, check pressures in the refrigerant circuit; if they are OK, check line connection between malfunctioning evaporator and line connection end at distribution point of refrigerant lines (for constrictions or blockage). If no malfunction can be determined, empty the refrigerant circuit and refill with the specified refrigerant quantity. Then check the pressures and the A/C system cooling output again; if the complaint still exists, replace the expansion valve that is prematurely switched by the questioned evaporator. Refer to Refrigerant Circuit (vehicle-specific service information).

Refer to REFRIGERANT CIRCUIT WITH IGNITION SWITCHED ON, CHECKING PRESSURE 

Test Requirements

NOTE:

The switching pressures for the activation of the A/C Compressor Regulator Valve -N280-, the A/C Clutch -N25- (if equipped) and the Radiator Fan -V7- are vehicle specific. Use the Vehicle Diagnostic Tester in the "Guided Fault Finding" function of the A/C system.

Pressures must be measured at the service connections; the component location for these connections are vehicle-specific. Refer to Refrigerant Circuit (vehicle-specific service information).

NOTE:

If the engine is not warm perform a road test.

For the cooling output test the engine must be warm but at an ambient temperature smaller than 25 °C (77 °F) a specific A/C system cooling output it is necessary that the engine and lower ambient temperatures are warm.

-- Start the engine.

-- Adjust the A/C system to maximum cooling output. Refer to the appropriate Cooling Output Checking Procedure in REPAIR INFORMATION (vehicle-specific service information).

NOTE:

The A/C compressor is driven by different components depending on the engine (belt or input shaft). The belt pulley or the drive unit has an overload protection to protect these components and the engine, which activates if the A/C compressor runs with resistance. Refer to A/C Compressor (vehicle-specific service information).

On vehicles with A/C Compressor Regulator Valve -N280- the control current can be read out in the measured values. Use the Vehicle Diagnostic Tester in the "Guided Fault Finding" function for the A/C system.

If A/C compressor is not driven with the engine running or regulating valve is not actuated:

-- Determine and eliminate cause for example by checking air conditioner DTC memory. Use the Vehicle Diagnostic Tester in the "Guided Fault Finding" function of the A/C system.

-- If equipped, check the power supply for the A/C Clutch - N25- if this is OK, service the A/C clutch. Refer to Refrigerant Circuit (vehicle-specific service information).

-- Check the activation of the A/C Compressor Regulator Valve -N280-. Use the Vehicle Diagnostic Tester in the "Guided Fault Finding" function of the A/C system.

NOTE:

On A/C compressors with a A/C Clutch -N25- the A/C compressor only works (delivers refrigerant) when near the A/C Compressor Regulator Valve -N280- the A/C Clutch A/C Clutch -N25- is also activated. Use the Vehicle Diagnostic Tester in the "Guided Fault Finding" function of the A/C system.

The A/C Compressor Regulator Valve A/C Compressor Regulator Valve -N280- (and the A/C Clutch A/C Clutch -N25-) is activated by the A/C Control Module -J301-, from the Front A/C Display Control Head -E87- or the Climatronic Control Module -J255- or a downstream control module. Use the Vehicle Diagnostic Tester in the "Guided Fault Finding" function of the A/C system and Refrigerant Circuit (vehicle-specific service information).

All of the test requirements marked with a * are vehicle-specific and described in the service information belonging to the vehicle. Refer to the appropriate Cooling Output Checking Procedure in REPAIR INFORMATION (vehicle-specific service information) and Refrigerant Circuit (vehicle-specific service information).

Adjustment for example on the Front A/C Display Control Head -E87- or the Climatronic Control Module -J255- or the A/C Control Module -J301- (and the Rear A/C Display Control Head -E265- on vehicles with two heater and A/C units)*. Refer to the appropriate Cooling Output Checking Procedure in REPAIR INFORMATION (vehicle-specific service information) and Component Location Overview - A/C System (vehicle-specific service information).

Setting on the Front A/C Display Control Head Front A/C Display Control Head -E87- / Climatronic Control Module Climatronic Control Module -J255- *. Refer to the appropriate Cooling Output Checking Procedure in REPAIR INFORMATION (vehicle-specific service information) and Component Location Overview - A/C System (vehicle-specific service information).

-- Preselect "Auto" mode (A/C compressor on).

-- Set temperature pre-selector switch to "cold" or "LO" for driver's side and front passenger's side (and left and right rear seats in vehicles with two heater and A/C units).

Adjustment on the A/C Control Module A/C Control Module -J301- *:

-- Press A/C button and rec- or recirculation button.

-- Turn temperature knob towards "cold" stop.

-- Position the fresh-air blower dial in the position "4" (maximum fresh air blower speed).

The following system test conditions should be met:

NOTE:

On specific versions the fan is switched on after the refrigerant circuit pressure specified value is exceeded. Use the Vehicle Diagnostic Tester in the "Guided Fault Finding" function of the A/C system.

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