Heat system on Grand Caravan

Diagnose and fix heat system on Grand Caravan

Heater box components

The heat system on the Grand Caravan includes blend door(s) and blend door actuator(s), re circulation door and actuator, mode air doors and mode door actuators, heater core, evaporator core, and an evaporator temperature sensor.

The blend door actuators mounted on the heater box. They are reversible, 12-volt DC servo motors. Single zone systems have a single blend-air door and dual zone systems have two.

The single zone blend door actuator is located on the driver side front heater box. On a dual zone system, that same blend door actuator is used to control the driver’s side temperature and a second blend door and actuator are mounted on the passenger side of the front heater box. The blend door(s) are calibrated by the AC HVAC control head

The same actuator is used for the mode air doors and the recirculation air doors, so there are interchangeable.

Blend door actuator operation

The blend door actuators word by toggling polarity from the HVAC head. Toggling polarity reverses the actuator’s direction. The HVAC control adjusts blend door actuator position by using 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 HVAC control head learns the blend-air door stop positions during the initial calibration procedure and stores a diagnostic trouble code (DTC) for any problems it detects in the blend door actuator circuits.

The actuators self calibrate in conjunction with the HVAC head when new units are installed or can be field calibrated using a scan tool. Other than the initial calibration or scan tool calibration, the blend actuators can’t be adjusted or repaired.

Mode door operation

The mode door actuator is operated by the HVAC head. The mode door actuator moves the floor/defrost and the panel-air doors in two directions. Like the blend door actuators, the HVAC head toggles voltage to make the mode doors move.

Testing the heat system on Grand Caravan

The HVAC control head self calibrates new actuators and self tests the actuators and sets a trouble code if an actuator or the wiring fails. A scan tool is required to perform a field calibration or monitor actuator operation

©, 2023 Rick Muscoplat