90S Quattro (Canada) V6-2.8L (AAH) (1993)
/v6-2.8l_(aah)/Page-805001.png)
A/C Compressor Signal: Description and Operation
PURPOSE
This signal is a communication link between the A/C control head, Engine Control Module (ECM) and the Transmission Control Module (TCM).
The signal is connected to pin C 10 of the ECM and is bidirectional (PIN C 10 - INPUT + OUTPUT).
OPERATION
Signal flow to or from the ECM is as follows:
SIGNAL IN
^
The A/C compressor clutch relay supplies voltage to pin C 10 via terminal 87A 140 milliseconds before the A/C clutch is engaged. The
ECM increases the idle air control valve opening to prevent an rpm drop when the compressor clutch engages.
SIGNAL OUT
^
The ECM sends a voltage signal to the A/C control head when the throttle valve is opened quickly (acceleration) while in first gear
(recognized from vehicle speed and engine speed). The A/C compressor is switched OFF for 3 to 12 seconds to aid in initial acceleration.
