A/C Signal: Description and Operation

A/C CLUTCH CONTROL RELAY
The A/C clutch control relay improves idle smoothness after engine start-up and also improves acceleration performance.

The A/C is cut off for approximately five seconds under the following conditions:
- just after the engine is started.
- when the Throttle Position (TP) sensor indicates a full throttle condition.

The A/C clutch control relay is located in the Constant Control Relay Module (CCRM) and cannot be serviced separately.

A/C CYCLING SWITCH
The Air Conditioning Cycling Switch (ACCS) provides a voltage signal input to the Powertrain Control Module (PCM) which indicates when the A/C is requested. When the A/C demand switch is turned ON, and both the A/C Cycling Switch and the high pressure contacts of the A/C Pressure Switch are closed, voltage is supplied to the ACCS circuit signal at the PCM.

If the ACCS signal is not received by the PCM, the Wide Open Throttle A/C Cut-off (WAC) circuit will not allow the A/C to operate.






A/C HIGH PRESSURE SWITCH
The A/C High Pressure Switch Is used for additional A/C system pressure control. The A/C High Pressure Switch is dual function for two-speed fan control applications.

For refrigerant containment control, the normally closed high pressure contacts open at a predetermined A/C pressure. This turns off the A/C by opening the A/C demand circuit, preventing the A/C pressure from rising to a level that would open the A/C High Pressure Relief Valve.

For fan control, the normally open medium pressure contacts close at a predetermined A/C pressure. This grounds the ACPSW circuit input to the PCM. The PCM will then turn on the high speed fan to help reduce the pressure.