A8 Sedan V8-3.7L (AEW) (1997)
Refrigerant: Testing and Inspection
A/C Refrigerant System (R-134A), Checking Pressures
Before checking refrigerant system pressures, check A/C system cooling performance. See: Heating and Air Conditioning/Testing and Inspection
Use high pressure service valve for checking system pressures.
Test Requirements
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Condenser and radiator clean and free of obstructions (clean if necessary)
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Drive belts for compressor and Generator in good condition and properly tensioned
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All air ducts, covers and seals OK and correctly installed
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Check DTC memory using VAG 1551 Scan Tool and eliminate/ repair any malfunctions indicated (not affecting A/C system)
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All air distribution flaps reach end positions
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Engine at normal operating temperature
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Evaporator housing and heater box do not leak air (draw in secondary air) at high fresh air blower speed
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Outside (ambient) temperature must be between 15 ° - 45 °C (59 ° - 113 °F)
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Engine running and system set to maximum cooling ("Auto" operating mode with "LO" temperature setting selected):
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Switch compressor ON (the warning light in the ECON button does not light up
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Temperature selection "LO" (for driver and passenger side)
If the compressor is activated (A/C clutch is switched ON)
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Fresh air blower -V2- runs
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Coolant fan -V7- runs (at least in stage 1)
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Closes back pressure door and opens recirculation door (within 1 minute after starting vehicle)
NOTES:
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With open recirculation door air flows out of outlets in the instrument panel even though the back pressure door is closed.
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If the air comes out of the instrument panel outlets, left and right heat regulating valves -N175- and -N176- of pump unit are closed and coolant
pump -V50- does not run (the heater cores are not warmed up).
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If one of the requirements is not met, check DTC memory and repair any malfunctions. See: Heating and Air Conditioning/Testing and Inspection
Preparation Work
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Check DTC memory and determine and repair all possible malfunctions.
Checking
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Switch ignition OFF.
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Connect high pressure hose of refrigerant recovery/recycling/recharging unit Kent-Moore ACR4, or equivalent, to high pressure service valve.
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Leave low pressure hose of refrigerant recovery/recycling/recharging unit disconnected.
NOTE: Only a high pressure service valve is used for A/C system servicing and checking pressures. A low pressure service valve is not installed
in the A/C system. Perform all A/C system pressure checks through the high pressure service valve.
Outside (ambient)
Base pressure in refrigerant
temperature 1)
system (engine OFF)
+15 °C (59 °F)
3.9 bar (56.5 psi)
+20 °C (68 °F)
4.7 bar (68.2 psi)
+25 °C (77 °F)
5.6 bar (81.2 psi)
+30 °C (86 °F)
6.7 bar (97.2 psi)
+35 °C (95 °F)
7.8 bar (113.1 psi)
+40 °C (104 °F)
9.1 bar (132.0 psi)
+45 °C (113 °F)
10.5 bar (152.3 psi)
1) All components of A/C system must be at the specified temperature for an accurate pressure measurement.
If A/C refrigerant system base pressure is less than specified on chart, system is low on refrigerant
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Check system for leaks using halogen leak detector Hitec HI400A-TEL or equivalent, repair system as necessary.
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Check pressure relief valve on A/C compressor.
If the pressure relief valve has blown:
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Check actuation of coolant fan according to wiring diagram.
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Check for pinched, kinked or damaged refrigerant lines/ hoses.
If no problems are found:
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Discharge refrigerant system, then evacuate and recharge.
If A/C refrigerant system pressure corresponds to or is higher than base pressure specified on chart