Electrical System

The electrical system consists of the following components:

• A/C blower motor.
• Blower speed switch (19986) .
• Blower on/off and clutch switch (integral with the air conditioner control (19980) assembly).
• Heater blower motor switch resistor (18591) with a thermal limiter.
• A/C cyclic switch (19E561).
• The magnetic A/C clutch (2884) .
• Fuses and wiring to complete the circuit.

The heater blower motor:

• Is installed in the A/C evaporator housing (19850) which is located under the A/C recirculating air duct (19C590) .
• The A/C blower motor and mounting flange are serviced as an assembly and should not be disassembled.

The blower (FAN) speed switch :

• Is mounted on the air conditioner control assembly.
• With the heater blower motor switch resistor , allows the selection of four A/C blower motor speeds.
• This switch does not turn the heater blower motor switch resistor off.

The heater blower motor switch resistor:

• Is installed in the rear face of the lower half of the A/C evaporator housing .
• Is located behind the glove compartment (06010) .
  • The A/C evaporator housing is used in conjunction with the blower speed switch to obtain the four A/C blower motor speeds.
• The heater blower motor switch resistor assembly also contains a thermal limiter which is used as a temperature protecting fuse.
  • The thermal limiter is located a preset distance from the resistor coils.
  • If the temperature of the thermal limiter reaches 121°C (250°F), the limiter contacts will open, interrupting the A/C blower motor circuit for all A/C blower motor speeds except HI.

The A/C cyclic switch and the A/C compressor clutch field coil (2987) are connected in series to control A/C compressor (19703) operation.

• The A/C cyclic switch is mounted on the suction accumulator/drier (19C836) .
• It closes when the pressure on the low side of the refrigerant system reaches approximately 310 kPa (45 psi).
• The A/C cyclic switch will open when the system pressure drops to approximately 172 kPa (25 psi).
• In ambient temperatures below approximately 7°C (45°F), the A/C cyclic switch will not allow compressor operation because of low system pressures.
• When the function selector lever is in either A/C position (MAX or NORM A/C), the radiator electric motor (8K621) is controlled by the opening and closing of the A/C cyclic switch .
• Power to the radiator electric motor is supplied through a constant control relay module (CCRM) as controlled by the A/C cyclic switch and the cooling fan temperature switch.
• If the engine coolant temperature exceeds approximately 105°C (221°F), the cooling fan temperature switch closes and the radiator electric motor will operate continuously until the engine coolant temperature drops below 105°C (221°F).

A/C Time Delay and WOT Cutout Switch

5.0L Engine

5.0L engines are equipped with a wide-open throttle (WOT) cutout switch to prevent A/C compressor operation during wide-open throttle operation.

• The WOT cutout switch is connected in series with the A/C time delay relay.
• It de-energizes the A/C time delay relay to stop A/C compressor operation.
• The A/C compressor will not operate as long as the WOT cutout switch is open.
• When the WOT cutout switch closes, the time delay relay continues to prevent A/C compressor operation for five seconds before allowing the A/C compressor to return to normal operation.
• The 5.0L WOT relay is located on the RH fender apron forward of the shock tower.

A cooling fan controller is used on all vehicles equipped with radiator electric motor , fan blade (8600) and fan shroud (8146) assembly.

• The cooling fan controller is used to cycle the engine radiator electric motor whenever the A/C compressor is operating.
• The controller also allows for engine cooling fan operation whenever the engine coolant temperature reaches 105°C (221°F).
• The cooling fan controller is located under the instrument panel (04320) to the left of the steering column.