Electrical System
The electrical system consists of the following components:^ Blower motor
^ Heater blower motor switch
^ A/C-heater function selector 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 (CCRM)
^ Powertrain Control Module (PCM)
^ Fuses to protect the circuits
^ System wiring
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 A/C 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 fan control is controlled during vehicle operation by the PCM through the CCRM. Fan control is energized under the following conditions:
^ Engine temperature is higher than normal. Fan control starts operating at 105°C (221°F) and stops when temperature drops to 94°C (200°F).
^ A/C is on and vehicle speed does not provide enough natural airflow. Fan control starts running at or below 69 km/h (43 mph) and stops at 77 km/h (48 mph).
^ The CCRM is located in the RH inner fender apron behind the inner fender splash shield.
The CCRM also controls A/C clutch operation based on signals received from the A/C cycling switch, the A/C pressure cut-off switch and the PCM.
^ 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 A/C manifold and tube.
^ The A/C cycling switch closes when the pressure on the low side of the refrigerant system rises to approximately 276-324 kPa (40-47 psi). The CCRM 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 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 CCRM 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 CCRM 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.
The CCRM 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 (WOT)
^ During low engine idle conditions
^ Excessively high engine temperature