RAM 1500 Truck 4WD V8-5.9L VIN Z (2002)
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 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.
