Part 2 of 6

LOSS OF CHARGE SWITCH - FRONT
This vehicle is equipped with a Loss of Charge Switch. This switch is screwed onto a fitting on the suction jumper line between the evaporator and the low side refrigerant system service port. The switch is used to measure if refrigerant system pressure goes too low. It is not responsible for cycling the A/C compressor clutch.

The loss of charge switch is connected in series electrically with the Heater-A/C controls between ground and the Powertrain Control Module (PCM). The switch contacts open and close causing the PCM to turn the compressor clutch ON and OFF. This prevents compressor operation when the system charge is low and prevents damage to the compressor. The switch opens with a pressure of 7 to 13 psi and closes when the pressure rises to 15 to 25 psi.

Fig. 16 A/C Pressure Transducer:

A/C PRESSURE TRANSDUCER - FRONT
This vehicle is equipped with an a/c pressure transducer. This transducer is screwed onto a fitting on the liquid line between the condenser and the high side refrigerant system service port.

The main function of the a/c pressure transducer is to disengage the compressor clutch when the refrigerant system high pressures are too high. The PCM senses a voltage from the transducer and converts it to a pressure. Based on this pressure, the PCM will disengage the clutch at 460 psi and re-engage the clutch at 290 psi. The a/c heater control also uses the pressure value to operate the auto-recirculation function for improved a/c performance under extreme conditions.

AMBIENT TEMP SENSOR - FRONT
Ambient air temperature is monitored by the compass mini-trip computer module through the ambient temperature sensor. The ambient temperature sensor is a variable resistor mounted to a bracket that is secured with a screw to the right side of the radiator yoke, behind the radiator grille and in front of the engine compartment.

For complete circuit diagrams, refer to Overhead Console in the Contents of Wiring Diagrams. The ambient temperature sensor cannot be adjusted or repaired and, if faulty or damaged, it must be replaced.

The ambient temperature sensor is a variable resistor that operates on a five-volt reference signal sent to it by the compass mini-trip computer module. The resistance in the sensor changes as temperature changes, changing the temperature sensor signal circuit voltage to the compass mini-trip computer module. Based upon the resistance in the sensor, the compass mini-trip computer module senses a specific voltage on the temperature sensor signal circuit, which it is programmed to correspond to a specific temperature.

BLEND DOOR ACTUATOR - FRONT
The blend door actuators are reversible, 12-volt Direct Current (DC), servo motors. Models with the single zone heater and air conditioner system have a single blend air door, which is controlled by a single blend door actuator. Models with the optional dual zone front heater and air conditioner system have dual blend air doors, which are controlled by two blend door actuators. The single zone blend door actuator is located on the driver side end of the heater-A/C housing unit, close to the dash panel. In the dual zone system, the same blend door actuator used for the single zone system becomes the passenger blend door actuator, and is mechanically connected to only the passenger side blend air door. In the dual zone system, a second separate blend door actuator is also located on the driver side end of the heater-A/C housing unit close to the instrument panel, and is mechanically connected to only the driver side blend air door.

The blend door actuators are interchangeable with each other, as well as with the actuators for the mode door and the recirculation air door. Each actuator is contained within an identical black molded plastic housing with an integral wire connector receptacle. Two integral mounting tabs allow the actuator to be secured with two screws to the heater-A/C unit housing. Each actuator also has an identical output shaft with splines that connects it to the link-age that drives the proper blend air door. The blend door actuators do not require mechanical indexing to the blend door linkage, as they are electronically calibrated by the heater-A/C control module. The blend door actuators cannot be adjusted or repaired and, if damaged or faulty, they must be replaced.

Each blend door actuator is connected to the heater-A/C control module through the vehicle electrical system by a dedicated two-wire take out and connector of the HAVC wire harness. The blend door actuator can move the blend air door in two directions. When the heater-A/C control module pulls the voltage on one side of the motor connection high and the other connection low, the blend air door will move in one direction. When the module reverses the polarity of the voltage to the motor, the blend air door moves in the opposite direction. When the module makes the voltage to both connections high or both connections low, the blend air door stops and will not move. These same motor connections also provide a feedback signal to the heater-A/C control module. This feedback signal allows the module to monitor the operation and relative positions of the blend door actuator and the blend air door. The heater-A/C control module learns the blend air door stop positions during the calibration procedure and will store a Diagnostic Trouble Code (DTC) for any problems it detects in the blend door actuator circuits. The blend door actuator can be diagnosed using a DRB III scan tool. Refer to the appropriate diagnostic information.

BLOWER MOTOR RESISTOR BLOCK - FRONT
During vehicle assembly, the blower motor resistor is mounted to the HVAC unit inside the passenger compartment. It can be accessed from the passenger foot well area. See Blower Motor Resistor in the Removal and Installation for more information.

Fig. 1 Rear Blower Motor Wheel/Resistor:

The blower motor resistor for the optional rear 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 located in the A/C control head directs the ground path through the correct resistor wire to obtain the selected blower motor speed.

The resistor has multiple resistor circuits 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 circuit 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 circuits. Each higher speed selected with the blower motor switch applies the blower motor ground path through fewer of the resistor circuits, increasing the blower motor speed.

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