DESCRIPTION

Fig. 7: Blend Door Actuators

The blend door actuators (1) for the front heating-A/C system are reversible, 12-volt direct current (DC) servo motors. Models with the front single zone heating-A/C system have a single blend-air door, which is controlled by a single blend door actuator. Models with the front dual zone heating-A/C system have dual blend-air doors, which are controlled by two blend door actuators.

The blend door actuator for the single zone heating-A/Csystem is located on the driver side front HVAC air distribution housing. For the dual zone heating-A/C system, the same blend door actuator used for the single zone system becomes the driver side blend door actuator, which is mechanically connected to only the driver side blend-air door. A second separate blend door actuator is also located on the passenger side of the front air distribution housing which is mechanically connected to only the passenger side blend-air door.

The blend door actuators are contained within a black molded plastic housing with an integral wire connector receptacle (2). An output shaft with splines (3) connect the blend door actuators to the blend door linkage. Three integral mounting tabs (4) allow the actuators to be secured to the air distribution housing. The blend door actuators do not require mechanical indexing to the blend door linkage, as they are electronically calibrated by the A/C-heater control.

The A/C-heater control must be recalibrated each time an actuator motor is replaced.

The blend door actuators are interchangeable with the actuators for the recirculation and mode-air doors.

OPERATION

The blend door actuators are connected to the A/C-heater control through the vehicle electrical system by a dedicated two-wire lead and connector. The blend door actuator(s) can move the blend-air door(s) 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 A/C-heater control uses a pulse-count positioning system to monitor the operation and relative position of the blend door actuator(s) and the blend-air door(s). The A/C-heater control 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 actuators are diagnosed using a scan tool.

The blend door actuators cannot be adjusted or repaired and must be replaced if inoperative or damaged.