Heater Mode

The left instrument panel fuse block provides power to the air temperature actuator through the ignition 3 voltage circuit. The HVAC control module receives power from two separate sources. The left instrument panel fuse block provides power to the 5-volt regulator inside the HVAC control module through the ignition 3 voltage circuit. The underhood junction block provides power to the HVAC control module through the battery positive voltage circuit. Ground is provided to the HVAC control module by the ground circuits through the right instrument panel junction block.

A 5-volt reference signal is sent out over the 5-volt reference circuit, through the right instrument panel junction block, to the air temperature actuator. When a desired temperature setting is selected, whether manual or automatic, a variable resistor is used to determine the air temperature door position sensor signals value. That varied 5-volt reference signal is sent back to the HVAC module software inside the HVAC control module on the air temperature door position sensor signal circuit. The HVAC control module uses this reference signal to determine the air temperature actuator position through the air temperature door motor supply voltage circuit. The motor opens the air mixture door to a position to divert sufficient air past the heater core to achieve the desired vehicle temperature. Ground is provided to the air temperature actuator by the ground circuits through the right instrument panel junction block.