K 2500 Truck 4WD V6-262 4.3L (1991)
A/C On Signal Diagnosis
A/C "ON" SIGNAL DIAGNOSIS
CIRCUIT AND TEST DESCRIPTION:
Turning on the air conditioning supplies CKT 59 battery voltage to the A/C compressor clutch and to terminal "B8"of the PCM connector to increase
idle air rate and maintain idle speed.
The PCM does not control the A/C compressor clutch, therefore, if A/C does not function, refer to HEATING VENTILATION AND AIR
CONDITIONING for diagnosis of the system.
If A/C is operating properly and idle speed dips too low when the A/C compressor turns "ON" or flares too high when the A/C compressor turns "OFF,"
check for an open CKT 59 to the PCM. If circuits are OK, it is a faulty PCM connector terminal "B8" or PCM.
Air Management Check (EAC Valve)
