Defrost stuck

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.

1. Disconnect and isolate the battery negative cable.
2. Remove the silencer from beneath the driverside end of the instrument panel.
3. Disconnect the hvac wire harness connector for the mode actuator from the actuator connector receptacle.
4. Remove the two screws that secure the mode actuator to the distribution housing.
5. Remove the mode actuator from the distribution housing.

Note: be sure to hold the mode cam and all mode door links in place.

Installation

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.

1. Position the mode actuator onto the heater/ac housing. If necessary, rotate the actuator slightly to align the splines on the actuator output shaft with those in the mode cam.

Note: be sure that the mode door links are positioned in the cam.

2. Install and tighten the two screws that secure the mode door actuator to the distribution housing. Tighten the screws to 2 nm (17 in. Lbs.).
3. Reconnect the hvac wire harness connector for the mode door actuator to the actuator connector receptacle.
4. Reinstall the silencer under the driver side end of the instrument panel.
5. Reconnect the battery negative cable.
6. Perform the heater-a/c control calibration procedure. The drm lll is used to perform the heater-a/c control calibration procedure.

See the diagram below for component locations

The A/C-heater control panel is a completely electronic control unit. Heater, Ventilation and Air Conditioning (HVAC) control module in integral with A/C-heater control panel. HVAC control module can communicate with other modules through PCI Bus communication network, and can be addressed using DRBIIIÂ or compatible generic scan tool. HVAC control module monitors ambient air temperature, evaporator temperature and electronic actuators that control air temperature and route airflow through front and rear HVAC housing (if equipped) to selected outlet vents.
To maintain accuracy, HVAC control module periodically performs a self-calibration test of actuator doors. HVAC control module records actuator revolutions required for full travel of each actuator door motor. Each actuator door can then be positioned by sending voltage pulse signals (in either polarity) to position actuator doors for maximum performance. This simplified method provides positive door positioning, without the complexity of vacuum actuators and feedback from position sensors. A/C system performance is checked using DRBIII or compatible generic scan tool and performing A/C cool down test. A/C cool down test will check the ability of the A/C refrigerant system to reduce evaporator core temperature -20°F (-29°C) within 2 minutes. If calibration or A/C cool down test fail, a DTC/fault message will be stored, and HVAC system performance will be lost. A/C-heater control panel (HVAC control module) is not serviceable, and if found faulty must be replaced as an assembly.