Part 1 of 2

BLOWER MOTOR
Front
The blower motor and blower wheel are located in the passenger side end of the heater-A/C housing, below the glove box. The blower motor controls the velocity of air flowing through the heater-A/C housing by spinning a squirrel cage-type blower wheel within the housing at the selected speed. The blower motor and blower wheel can only be serviced with the heater-A/C housing removed from the passenger compartment.

The blower motor will only operate when the ignition switch is in the ON position, and the heater-A/C mode control switch knob is in any position, except Off. The blower motor receives a fused battery feed through the blower motor relay (Voltage Reduction Relay or VRR) whenever the ignition switch is in the ON position.

The blower motor battery feed circuit is protected by a fuse in the Power Distribution Center (PDC). The blower motor relay control circuit is protected by a fuse in the junction block. Blower motor speed is controlled by regulating the ground path through the heater-A/C mode control switch, the blower motor switch, the blower motor resistor, the blower motor relay (VRR), and the high speed blower motor relay.

The blower motor and blower motor wheel cannot be repaired and, if faulty or damaged, they must be replaced. The blower motor and blower wheel are each serviced separately.

Rear
The rear blower motor and blower wheel are mounted to a blower wheel housing located inside the rear overhead A/C unit, above the headliner. The blower motor controls the velocity of air flowing through the overhead A/C unit by spinning a wide squirrel cage-type blower wheel within the housing at the selected speed. Rear blower motor speed is controlled by regulating the ground path through the rear blower motor switch and the rear blower motor resistor.

The rear blower motor will only operate when the ignition switch is in the ON position. The rear blower motor receives a fused battery feed through a fuse in the relay and fuse block whenever the ignition switch is in the ON position. The relay and fuse block is attached to the back of the junction block, under the left side of the instrument panel in the passenger compartment.

The rear blower motor, blower wheel, and blower wheel housing cannot be repaired and, if faulty or damaged, they must be replaced as a complete factory-balanced unit.

BLOWER MOTOR RELAY
The blower motor relay (also referred to as Voltage Reduction Relay or VRR) is an International Standards Organization (ISO)-type relay. The relay is an electromechanical device that switches battery current from a fuse in the Power Distribution Center (PDC) directly to the blower motor. The relay is energized when the relay coil is provided a voltage signal by the ignition switch. This arrangement reduces the amount of battery current that must flow through the ignition switch.

The blower motor relay control circuit is protected by a fuse located in the junction block. When the relay is de-energized, the blower motor receives no battery current. The VRR is used to reduce blower speeds in Heat mode. In non-A/C modes, the relay is de-energized and switches the current flow through an added resistance in the resistor block. When an A/C mode is selected, the relay is energized and the normally open contact is used to bypass the added resistor. The fuse is located in the small relay fuse block that is attached to the Junction Block. The relay is energized by grounding the coil low side with the HVAC switch in any A/C mode. See Blower Motor Relay for more information.

Blower Motor Relay (VRR) Location:

The blower motor relay is mounted with a single screw directly to the instrument panel's structural plastic inside the glove box opening, next to the left-side energy-absorbing bracket. Refer to the PDC label for blower motor relay identification and location.

The blower motor relay (VRR) cannot be repaired and, if faulty or damaged, it must be replaced.

BLOWER MOTOR RESISTOR

Blower Motor Resistor - Factory Installation:

Front
During vehicle assembly, the blower motor resistor is mounted to the dash plenum panel inside the passenger compartment prior to instrument panel roll-up. However, a resistor mounting plate has been designed so that the resistor can be removed through an access hole in the cowl plenum panel just below the windshield. It can be accessed by removing the cowl plenum cover/grille panel.

The resistor has multiple resistor wires, each of which will change the resistance in the blower motor ground path to change the blower motor speed. The blower motor switch directs the ground path through the correct resistor wire to obtain the selected blower motor speed.

With the blower motor switch in the lowest speed position, the ground path for the motor is applied through all of the resistor wires. Each higher speed selected with the blower motor switch applies the blower motor ground path through fewer of the resistor wires, increasing the blower motor speed. When the blower motor switch is in the highest speed position, the blower motor resistor is bypassed and the blower motor receives a direct path to ground through the high speed blower motor relay.

The blower motor resistor cannot be repaired and, if faulty or damaged, it must be replaced.

Rear
The blower motor resistor for the optional rear overhead A/C unit is located within the unit housing. The resistor has multiple resistor wires, each of which will change the resistance in the blower motor ground path to change the blower motor speed. The blower motor switch directs the ground path through the correct resistor wire to obtain the selected blower motor speed.

With the blower motor switch in the lowest speed position, the ground path for the motor is applied through all of the resistor wires. Each higher speed selected with the blower motor switch applies the blower motor ground path through fewer of the resistor wires, increasing the blower motor speed. When the blower motor switch is in the highest speed position, the blower motor resistor is bypassed and the blower motor receives a direct path to ground.

The blower motor resistor cannot be repaired and, if faulty or damaged, it must be replaced.

BLOWER MOTOR SWITCH
Front
The heater-A/C blower mot9r is controlled by a four position rotary-type blower motor switch, mounted in the heater-A/C control panel. The switch allows the selection of one of four blower motor speeds, but can only be turned OFF by selecting the OFF position with the heater-A/C mode control switch knob.

The blower motor switch directs the blower motor ground path through the mode control switch to the blower motor resistor, or directly to ground through the high speed blower motor relay, as required to achieve the selected blower motor speed.

The blower motor switch cannot be repaired and, if faulty or damaged, the entire heater-A/C control unit must be replaced. The blower motor switch knob is serviced separately.

Rear
The optional rear overhead A/C unit blower motor is controlled by a four position rotary-type blower motor switch, mounted by a snap fit in a hole in the headliner over the right front seat back. The switch allows the selection of one of three blower motor speeds and an OFF position. The blower motor switch directs the blower motor ground path through the blower motor resistor.

The blower motor switch cannot be repaired and, if faulty or damaged, the entire switch unit must be replaced. The blower motor switch has a replaceable incandescent-type illumination lamp bulb.

COMPRESSOR
The air conditioning system uses a Sanden SD7H15 seven cylinder, reciprocating wobble plate- type compressor on all models. This compressor has a fixed displacement of 150 cubic centimeters (9.375 cubic inches), and has both the suction and discharge ports located on the cylinder head. A label identifying the use of R-134a refrigerant is located on the compressor.

The compressor is driven by the engine through an electric clutch, drive pulley and belt arrangement. The compressor is lubricated by refrigerant oil that is circulated throughout the refrigerant system with the refrigerant.

The compressor draws in low-pressure refrigerant vapor from the evaporator through its suction port. It then compresses the refrigerant into a high-pressure, high-temperature refrigerant vapor, which is then pumped to the condenser through the compressor discharge port.

The compressor cannot be repaired. If faulty or damaged, the entire compressor assembly must be replaced. The compressor clutch, pulley and clutch coil are available for service.

COMPRESSOR CLUTCH

Compressor Clutch - Typical:

The compressor clutch assembly consists of a stationary electromagnetic coil, a hub bearing and pulley assembly, and a clutch plate. The electromagnetic coil unit and the hub bearing and pulley assembly are each retained on the nose of the compressor front housing with snap rings. The clutch plate is mounted to the compressor shaft and secured with a nut.

These components provide the means to engage and disengage the compressor from the engine serpentine accessory drive belt. When the clutch coil is energized, it magnetically draws the clutch into contact with the pulley and drives the compressor shaft. When the coil is not energized, the pulley freewheels on the clutch hub bearing, which is part of the pulley. The compressor clutch and coil are the only serviced parts on the compressor.

The compressor clutch engagement is controlled by several components: the heater-A/C mode control switch, the electronic cycling clutch switch, the low pressure cut-off switch, the high pressure cut-off switch, the compressor clutch relay, and the Powertrain Control Module (PCM). The PCM may delay compressor clutch engagement for up to thirty seconds.

COMPRESSOR CLUTCH RELAY
The compressor clutch relay is an International Standards Organization (ISO) micro-relay. The terminal designations and functions are the same as a conventional ISO relay. However, the micro-relay terminal orientation (footprint) is different, the current capacity is lower and the relay case dimensions are smaller than those of the conventional ISO relay.

The compressor clutch relay is an electromechanical device that switches battery current to the compressor clutch coil when the Powertrain Control Module (PCM) grounds the coil side of the relay. The PCM responds to inputs from the heater-A/C mode control switch, the electronic cycling clutch switch, the low pressure cut-off switch, and the high pressure cut-off switch.

The compressor clutch relay is located in the Power Distribution Center (PDC) in the engine compartment. Refer to the PDC label for relay identification and location.

The compressor clutch relay cannot be repaired and, if faulty or damaged, it must be replaced.

CONDENSER
The condenser is located in the air flow in front of the engine cooling radiator. The condenser is a heat exchanger that allows the high-pressure refrigerant gas being discharged by the compressor to give up its heat to the air passing over the condenser fins.

When the refrigerant gas gives up its heat, it condenses. When the refrigerant leaves the condenser, it has become a high-pressure liquid refrigerant. The volume of air flowing over the condenser fins is critical to the proper cooling performance of the air conditioning system. Therefore, it is important that there are no objects placed in front of the radiator grille openings in the front of the vehicle or foreign material on the condenser fins that might obstruct proper air flow. Also, any factory-installed air seals or shrouds must be properly reinstalled following radiator or condenser service.

The condenser cannot be repaired and, if faulty or damaged, it must be replaced.

ELECTRONIC CYCLING CLUTCH SWITCH
The Electronic Cycling Clutch Switch (ECCS) is mounted to the outboard side of the thermal expansion valve in the engine compartment. A thermistor probe within a capillary tube on the switch is inserted into a well on the side of the expansion valve filled with a thermally-conductive grease. This arrangement allows the ECCS to monitor the temperature of the expanded refrigerant entering the evaporator.

The function of the ECCS is to prevent refrigerant temperatures from becoming so low that condensation freezes on the evaporator fins. This condition is referred to as evaporator icing. Evaporator icing reduces air conditioning system air flow and cooling performance.

The ECCS is connected in series electrically with the heater-A/C mode control switch, the low pressure cut-off switch and the high pressure cut-off switch between ground and the Powertrain Control Module (PCM). The ECCS will open when it monitors a refrigerant temperature below about 2.9 °C (37.2 °F), and will close again when the refrigerant temperature reaches about 4.3 °C (39.7 °F). The opening and closing of the ECCS signals the PCM to cycle the compressor clutch on and OFF through the compressor clutch relay.

The ECCS is a factory sealed and calibrated unit and cannot be adjusted or repaired. If faulty or damaged, the ECCS must be replaced.

EVAPORATOR COIL
Front
The evaporator coil is located in the heater-A/C housing, under the instrument panel. The evaporator coil is positioned in the heater-A/C housing so that all air that enters the housing must pass over the fins of the evaporator before it is distributed through the system ducts and outlets. However, air passing over the evaporator coil fins will only be conditioned when the compressor is engaged and circulating refrigerant through the evaporator coil tubes.

Refrigerant enters the evaporator from the expansion valve as a low-temperature, low-pressure mixture of liquid and gas. As air flows over the fins of the evaporator, the humidity in the air condenses on the fins, and the heat from the air is absorbed by the refrigerant. Heat absorption causes the refrigerant to boil and vaporize. The refrigerant becomes a low-pressure gas when it leaves the evaporator.

The evaporator coil cannot be repaired and, if faulty or damaged, it must be replaced.

Rear
The rear evaporator coil is located in the rear overhead A/C unit housing, above the headliner. The evaporator coil is positioned in the overhead A/C unit housing so that all air that enters the housing must pass over the fins of the evaporator before it is distributed through the system outlets. However, air passing over the evaporator coil fins will only be conditioned when the compressor is engaged and circulating refrigerant through the evaporator coil tubes.

Refrigerant enters the evaporator from the rear expansion valve as a low-temperature, low-pressure mixture of liquid and gas. As air flows over the fins of the evaporator, the humidity in the air condenses on the fins, and the heat from the air is absorbed by the refrigerant. Heat absorption causes the refrigerant to boil and vaporize. The refrigerant becomes a low-pressure gas when it leaves the evaporator.

The rear evaporator coil cannot be repaired and, if faulty or damaged, the rear evaporator coil must be replaced.

EXPANSION VALVE
Front
The front "H" valve-type thermal expansion valve (TXV) is located at the dash panel between the liquid and suction lines, and the evaporator coil. High-pressure, high temperature liquid refrigerant from the liquid line passes through the expansion valve orifice, converting it into a low-pressure, low-temperature mixture of liquid and gas before it enters the evaporator coil.

A sensor in the expansion valve control head monitors the temperature and pressure of the refrigerant leaving the evaporator coil through the suction line, and adjusts the orifice size at the liquid line to let the proper amount of refrigerant into the evaporator coil to meet the vehicle cooling requirements. Controlling the refrigerant flow through the evaporator ensures that none of the refrigerant leaving the evaporator is still in a liquid state, which could damage the compressor.

The expansion valve is a factory calibrated unit and cannot be adjusted or repaired. If faulty or damaged, the expansion valve must be replaced.

Rear
Vehicles equipped with the optional rear overhead A/C unit have an H-type thermal expansion valve (TXV) located underneath the passenger side of the vehicle floor panel, next to the sill. It performs the same function as the front expansion valve, to monitor refrigerant temperature and pressure at the control head and meter the refrigerant entering the evaporator to meet the vehicle cooling requirements.

The rear expansion valve is a factory calibrated unit and cannot be adjusted or repaired. If faulty or damaged, the rear expansion valve unit must be replaced.

FILTER-DRIER
The filter-drier is mounted on the right front wheelhouse front extension in the engine compartment, in the liquid line between the condenser outlet and the evaporator inlet. Refrigerant enters the filter-drier as a high-pressure, high-temperature liquid

The filter-drier performs a filtering action to prevent foreign material in the refrigerant from contaminating the expansion valve. A desiccant bag is mounted inside the filter-drier canister to absorb any moisture which may have entered and become trapped within the refrigerant system. In addition, during periods of high demand air conditioner operation, the filter-drier acts as a reservoir to store surplus refrigerant.

The filter-drier cannot be repaired. If the filter-drier is faulty or damaged, or if the refrigerant system has been contaminated or left open to the atmosphere for an indeterminable period, it must be replaced.