Test M: The A/C Is Always On

PINPOINT TEST M: THE A/C IS ALWAYS ON

M1-M4:

M4-M7:

M7-M8:

Normal Operation
Under normal operation, in vehicles equipped with a manual climate control system, when A/C is requested, voltage is sent from the function selector switch to the evaporator discharge air temperature sensor through circuit 348 (VT). In vehicles equipped with electronic automatic temperature control (EATC), ignition voltage is provided to the evaporator discharge air temperature sensor through circuit 296 (WH/VT)/348 (VT).

Voltage is sent from the evaporator discharge air temperature sensor to the low charge protection switch through circuit 1932 (OG/LB). The evaporator discharge air temperature sensor is grounded through circuit 875 (BKLB). Voltage is sent from the low charge protection switch to the A/C high pressure switch through circuit 441 (RD/YE). Voltage is sent from the A/C high pressure switch to the powertrain control module (PCM) through circuit 439 (TN/RD).

The PCM provides a ground for the A/C clutch relay coil through circuit 331 (PK/YE). The A/C clutch relay coil receives ignition voltage through circuit 391 (RD/YE). Ignition voltage for the A/C clutch relay switch is provided through circuit 883 (PK/LB). When the relay is energized, ignition voltage is supplied to the A/C clutch solenoid through circuit 321 (GY/WH). Ground is supplied for the A/C clutch solenoid through circuit 57 (BK).

Possible Causes
- A short to ground in circuit 331 (PK/YE)
- A short to voltage in circuits 321 (GY/WH), 348 (VT), 441 (RD/YE), 439 (TN/RD) or 1932 (OG/LB)
- Powertrain control module (PCM)
- Electronic automatic temperature control (EATC) module
- Function selector switch
- A/C control relay
- A/C clutch air gap