90CS Quattro V6-2.8L (AAH) (1994)
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A/C Compressor Signal: Testing and Inspection
A/C Compressor Cut-Out Signal
CHECKING A/C COMPRESSOR CUT-OUT.
During acceleration from a stop and from low speed, the A/C compressor is switched off for approx. 12 seconds. If the accelerator pedal is
released sooner, the time decreases to a minimum of 3 seconds.
TEST CONDITIONS
^
A/C function OK
^
No codes stored in DTC memory
^
Vehicle at room temperature, i.e. warmer than 15°C (59°F)
TEST PROCEDURES
-
Start engine and let idle.
-
Switch A/C on (manual A/C) or, with automatic A/C, press buttons "AUTO", temperature "LO" and blower speed "HI."
^
Compressor symbol must light up
^
A/C compressor must run
-
Using VAG 1551 scan tool, initiate "Basic Setting" function 04, display group 000.
^
A/C compressor must stop (check visually)
If A/C compressor does stop:
-
Switch A/C off, let engine continue to idle.
-
Using VAG 1551 scan tool, initiate "Read Measuring Value Block" function 08, display group 004.
-
Display will appear as shown:
Read Measuring Block Value 4
1 2 3 4
-
Observe the second digit of 4-digit display (switch inputs) in display field 4.
^
Specified value: X0X X
NOTE:
The switch inputs indicated by digits 1, 3 and 4 are ignored for this test.
-
Switch A/C on (manual A/C) or, with automatic A/C, press buttons "AUTO", temperature "LO" and blower speed "HI."
^
Specified value: X1X X (zero changes to one)
-
Press "arrow" button.
If specified values are obtained:
-
Press -0- and -6- buttons to select "End Output" function 06.
-
Press -Q- button to confirm input.
If the display does not change A/C settings may be incorrect, proceed as follows:
-
Check continuity of wiring and/or short circuit using wiring diagram as follows:
For manual A/C:
-
Check wiring between ECM connector C terminal 10 and A/C clutch control module -J153-.
For automatic A/C:
-
Check wiring between ECM connector C terminal 10 and A/C control head -E87-.
If no malfunctions are found in wiring:
-
Check A/C system.
If "X1X X" is displayed:
-
Briefly push accelerator pedal to wide open throttle position.
^
Display must briefly change to XOX X and, after releasing accelerator pedal, change back to X1X X.
If the values change as described:
-
Check whether compressor is switched off when depressing accelerator pedal suddenly (visual inspection).
If the compressor is not switched off:
