No air flow when set on defrost

Hi,

If you have no air flow from the defroster, most likely there is an issue with what is called the mode door actuator.

If you look at pic 1, it shows the actuator I am referring to. Also, here are the directions for removal and replacement of the actuator. The additional attached pics correlate with the directions.

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2008 Chrysler Truck Aspen 4WD V8-5.7L
Front Controls
Vehicle Heating and Air Conditioning Air Door Actuator / Motor Service and Repair Removal and Replacement Mode Door Actuator - Removal Front Controls
FRONT CONTROLS
REMOVAL

WARNING: On vehicles equipped with airbags, disable the airbag system before attempting any steering wheel, steering column, or instrument panel component diagnosis or service. Disconnect and isolate the battery negative (ground) cable, then wait two minutes for the airbag system capacitor to discharge before performing further diagnosis or service. This is the only sure way to disable the airbag system. Failure to take the proper precautions could result in accidental airbag deployment and possible personal injury or death.

Pic 2

1. Disconnect and isolate the negative battery cable.
2. Remove the screws (5) that secure the panel door actuator (2) and the floor/defrost door actuator (3) located on the driver side end of the HVAC housing (4) as required.
3. Disconnect the HVAC wire harness connector (1) from the panel door actuator and the floor/defrost door actuator as required.
4. Remove the mode door actuator(s) from the HVAC housing.

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2008 Chrysler Truck Aspen 4WD V8-5.7L
Front Controls
Vehicle Heating and Air Conditioning Air Door Actuator / Motor Service and Repair Removal and Replacement Mode Door Actuator - Installation Front Controls
FRONT CONTROLS
INSTALLATION

pic 3

1. Position the mode door actuator(s) (1) onto the driver side end of the HVAC housing as required. If necessary, rotate the actuator slightly to align the splines on the actuator output shaft with those in the mode-air door linkage.

Pic 4

2. Install the screws (5) that secure the panel door actuator (2) and the floor/defrost door actuator (3) to the HVAC housing (4) as required. Tighten the screws to 2 Nm (17 in. Lbs.).
3. Connect the HVAC wire harness connector (1) to the mode door actuator(s) as required.
4. Reconnect the negative battery cable.
5. Initiate the Actuator Calibration function using a scan tool See: Heating and Air Conditioning > Component Tests and General Diagnostics > HVAC System Test or See: Heating and Air Conditioning > Component Tests and General Diagnostics > HVAC System Test.

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Before just replacing the actuator, see if it moves when you adjust from floor to defrost. If it doesn't, replace it. Also, I hope I understood your post. At first you said there is no air flow through the defroster, but later in the post it almost seemed to be only temperature related. The directions are for air flow and not temp, so if I am wrong, let me know.

Let me know if this helps or if you have other questions.

Joe