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Home >> GMC >> 2003 >> Safari Van Cargo, AWD >> Repair and Diagnosis >> External Pages >> Different car >> Section 1650 (HVAC System - Automatic) >> Diagnostic Information and Procedures >> DTC B0228, B0423, or B3779 >> Circuit/System Description

Circuit/System Description

WARNING: This page is about a different car, the 2009 Saturn Vue. However, it is still accessible from the selected car via links, so may be relevant.

The actuators operate using 5 circuits. A 5-volt reference, low reference, signal circuit and two bi-directional 0 or 12 volt control circuits. The HVAC control module supplies a low reference and 5-volt reference to the potentiometer. The HVAC control module monitors the voltage drop across the potentiometer on the door position signal circuit. As the actuator door changes position the door position signal circuit voltage also changes. The two bi-directional control circuits enable the actuator to operate. Both circuits are set to 0 volts when the HVAC control module detects, from the feedback potentiometer, that the actuator is in the desired position. In order to move the actuator, the HVAC control module switches the appropriate control circuit to 12 volts.

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