Operation CHARM: Car repair manuals for everyone.
Home >> Dodge or Ram Truck >> 2003 >> RAM 3500 Truck 2WD V10-8.0L VIN W >> Repair and Diagnosis >> Heating and Air Conditioning >> Description and Operation >> A/C Controls >> Part 2 of 2

Part 2 of 2

BLEND DOOR ACTUATOR
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 driver side blend door actuator, and is mechanically connected to only the driver side blend air door. In the dual zone system, a second separate blend door actuator is also located on the top of the heater-A/C housing unit and is mechanically connected to only the passenger 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 linkage 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 HVAC 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 RELAY
The blower motor relay is a International Standards Organization (ISO)-type relay The relay is a 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.

The blower motor relay is installed in a wire harness connector that is secured to the passenger side outboard end of the HVAC housing in the passenger compartment, next to the HVAC wire harness connector.

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

BLOWER MOTOR RESISTOR BLOCK
The blower motor resistor is mounted to the rear side of the HVAC housing on the passenger side of the vehicle.

The resistor is a ceramic resistor that utilizes resistor circuit tracers to reduce current flow to the blower. The blower motor switch directs the ground path through the correct resistor circuit to obtain the selected speed.

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

BLOWER MOTOR SWITCH
The A/C Heater blower motor is controlled by a four position rotary-type blower motor switch, mounted in the A/C Heater 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 on the blower motor switch.

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

The blower motor switch cannot be repaired and, if faulty or damaged, the entire A/C Heater control unit must be replaced.

Fig. 17 HVAC Housing - Dual Zone Shown (Typical - Single Zone):




MODE DOOR ACTUATOR
The mode door actuator is a reversible, 12-volt Direct Current (DC), servo motor. The single mode door actuator is located on the driver side end of the heater-A/C housing unit, close to the top of the distribution housing. The mode door actuator is mechanically connected to the mode door. The mode door actuator is interchangeable with the actuators for the blend air door(s) 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 linkage that drives the mode door. The mode door actuator does not require mechanical indexing to the mode door linkage, as it is electronically calibrated by the heater-A/C control module. The mode door actuator cannot be adjusted or repaired and, if damaged or faulty, it must be replaced.

The mode 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 HVAC wire harness. The mode door actuator can move the mode 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 mode door will move in one direction. When the module reverses the polarity of the voltage to the motor, the mode door moves in the opposite direction. When the module makes the voltage to both connections high or both connections low, the mode 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 position of the mode door actuator and the mode door. The heater-A/C control module learns the mode door stop positions during the calibration procedure and will store a Diagnostic Trouble Code (DTC) for any problems it detects in the mode door actuator circuits. The mode door actuator can be diagnosed using a DRB III scan tool. Refer to the appropriate diagnostic information.

RECIRCULATION DOOR ACTUATOR
The recirculation door actuator is a reversible, 12-volt Direct Current (DC), servo motor. The single recirculation door actuator is located on the passenger side end of the heater-A/C housing unit. The recirculation door actuator is mechanically connected to the recirculation air door. The recirculation door actuator is interchangeable with the actuators for the blend air door(s) and the mode doors. 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 intake air housing. Each actuator also has an identical output shaft with splines that connects it to the linkage that drives the recirculation air door. The recirculation door actuator does not require mechanical indexing to the recirculation air door, as it is electronically calibrated by the heater-A/C control module. The recirculation door actuator cannot be adjusted or repaired and, if damaged or faulty, it must be replaced.

The recirculation 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 HVAC wire harness. The recirculation door actuator can move the recirculation 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 recirculation air door will move in one direction. When the module reverses the polarity of the voltage to the motor, the recirculation air door moves in the opposite direction. When the module makes the voltage to both connections high or both connections low, the recirculation 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 position of the recirculation door actuator and the recirculation air door. The heater-A/C control module learns the recirculation air door stop positions during the calibration procedure and will store a Diagnostic Trouble Code (DTC) for any problems it detects in the recirculation door actuator circuits. The recirculation door actuator can be diagnosed using a DRB III scan tool. Refer to the appropriate diagnostic information.

pro multis · About Operation CHARM