Relays/Switches

RELAYS/SWITCHES
The manual A/C-heater electrical system uses a number of relays and pressure sensitive switches to control system functions. These components are:
- A/C clutch control relay
- the A/C wide open throttle (WOT) relay
- the A/C pressure cut-off switch
- the A/C cycling switch
- the A/C-heater blower relay

The A/C WOT relay controls A/C clutch operation with the A/C clutch control relay. The A/C cycling switch, A/C pressure cut-off switch and the powertrain control module together control the A/C WOT relay.

- The A/C cycling switch and A/C pressure cut-off switch are connected in series.
- The A/C cycling switch is mounted on the suction accumulator/drier.
- The A/C pressure cut-off switch is mounted to the condenser to evaporator tube.
- The A/C cycling switch closes when the pressure on the low side of the refrigerant system reaches approximately 310 kPa (45 psi). The A/C WOT relay will then engage the A/C clutch.
- The A/C cycling switch will open when the system pressure drops to approximately 172 kPa (25 psi) disengaging the A/C clutch.
- In ambient temperatures below approximately 7°C (45°F), the A/C cycling switch will not allow operation of the A/C compressor because of low system pressures.
- The A/C pressure cut-off switch is used on all vehicles to interrupt operation of the A/C compressor in the event of high system discharge pressures.
- When compressor head pressure rises to 2861-3068 kPa (415-455 psi), the contacts open and the A/C WOT relay will de-energize the A/C clutch control relay and disengage the A/C clutch.
- When head pressure drops to 1517-1931 kPa (220-280 psi), the contacts again close and allow operation of the A/C clutch.

The switch contains a second set of electrical contacts for the engine cooling fan motor which are normally open.
- When discharge line pressure reaches 1965-2172 kPa (286-315 psi), these contacts close and will engage the engine cooling fan motor.
- When pressure drops to approximately 1724 kPa (250 psi), the contacts again open and the engine cooling fan motor is disengaged.

The A/C WOT relay de-energizes the A/C clutch control relay and deactivates the A/C clutch when signalled by the powertrain control module. The A/C clutch could be deactivated in this manner under the following conditions:
- engine start-up
- wide open throttle
- during low engine idle conditions
- excessively high engine temperatures

The A/C-heater blower relay controls the power supply to the heater blower motor switch.
- The A/C damper door switch energizes the A/C-heater blower relay in all function selector positions except OFF.
- Energizing the A/C-heater blower relay supplies power to the heater blower motor switch and allows selection of the four blower motor speeds.