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Home >> GMC >> 2006 >> Sierra 1500 HD, 4WD >> Repair and Diagnosis >> External Pages >> Different car >> Section 868 (HVAC System - Manual) >> Description and Operation >> Air Delivery Description and Operation >> Air Delivery >> Front Control

Front Control

WARNING: This page is about a different car, the 2007 GMC Sierra and 2007 Chevrolet Silverado. However, it is still accessible from the selected car via links, so may be relevant.

The HVAC control module controls the distribution of air by the use of recirculation and mode actuators. The modes that may be selected are:

The mode actuator is connected to the mode door by a cam type linkage system. Depending on the position of the door, air is directed through the HVAC module and distributed through various ducts leading to the outlets in the dash. If a fault is detected within the mode door travel, the HVAC control module will drive the actuator to defrost, which is a default position for the mode door actuator. Turning the mode door position to either defrost or defog positions, the HVAC control module will move the recirculation actuator to outside air reducing window fogging. When defrost/defog is selected, the A/C compressor is activated. The A/C compressor clutch will engage when ambient temperatures are above 3°C (38°F). A/C is available in all modes. Recirculation is only available in Panel and Bi-Level modes. The rear window defogger does not affect the HVAC system.