RAM 2500 Truck 2WD V8-5.7L VIN D (2004)
Air Door Actuator / Motor: Description and Operation
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 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 doors, which are controlled by two blend door actuators. The single zone blend door actuator is located on the driver side end of the HVAC
housing, 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 door. In the dual zone system, a second separate blend door actuator is also
located on the top of the HVAC housing and is mechanically connected to only the passenger side blend door.
The blend door actuators are interchangeable with each other, as well as with the actuators for the mode door, defrost door and the recirculation door.
Each actuator is contained within an identical black molded plastic housing with an integral wire connector receptacle. Integral mounting tabs allow the
actuator to be secured with three screws to the HVAC housing. Each actuator also has an identical output shaft with splines that connects it to the linkage
that drives the proper 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 A/C heater control through the vehicle electrical system by a dedicated two-wire lead and connector from
the HVAC wire harness. The blend door actuator can move the blend-air door in two directions. When the A/C-heater control 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 A/C-heater control reverses the
polarity of the voltage to the motor, the blend-air door moves in the opposite direction. When the A/C-heater control makes the voltage to both
connections high or both connections low, the blend-air door stops and will not move. The motor connections also provide a feedback signal to the
A/C-heater control. This feedback signal allows the A/C-heater control to monitor the operation and relative positions of the blend door actuator and the
blend-air door. The A/C-heater control learns the blend 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 DRBIII(R) scan tool. Refer to Body Diagnostic Procedures for more information. The blend door
actuators cannot be adjusted or repaired and, if damaged or faulty, they must be replaced.
