Electrical System

The electrical system consists of the following components:
- blower motor
- heater blower motor switch
- A/C damper door switch
- heater blower motor switch resistor with a thermal limiter
- A/C pressure cut-off switch
- A/C cycling switch
- A/C clutch
- constant control relay module
- Powertrain Control Module (PCM)
- fuses and wiring to complete the circuit The blower motor is installed in the A/C evaporator housing.

The heater blower motor switch:
- is mounted on the A/C control assembly.
- with the heater blower motor switch resistor, allows the selection of four blower motor speeds.

The heater blower motor switch resistor:
- is installed in the A/C evaporator housing.
- contains a thermal limiter which is used as a temperature protecting fuse.

The constant control relay module controls A/C compressor and engine cooling fan motor operation based on information received from the A/C cycling switch, the A/C pressure cut-off switch and the powertrain control module.
- 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 discharge line.
- The A/C cycling switch closes when the pressure on the low side of the refrigerant system reaches approximately 276-324 kPa (40-47 psi). The constant control relay module will then engage the A/C clutch.
- The A/C cycling switch will open when the system pressure drops to approximately 152-193 kPa (22-28 psi), disengaging the A/C clutch.
- In ambient temperatures below approximately 7-10°C (45-50°F), the A/C cycling switch will not allow compressor operation because of low system pressures.
- The A/C pressure cut-off switch is used on all vehicles to interrupt A/C compressor operation in the event of high system discharge pressures.
- When compressor head pressure rises to approximately 2896 kPa (420 psi), the contacts open and the constant control relay module will disengage the A/C clutch.
- When head pressure drops to approximately 1724 kPa (250 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 approximately 2241 kPa (325 psi), these contacts close and the constant control relay module will engage the engine cooling fan motor.
- When pressure drops to approximately 1896 kPa (275 psi), the contacts again open and the engine cooling fan motor is disengaged.