C 3500 Truck 2WD V8-6.0L VIN U (2001)
Air Door Actuator / Motor: Description and Operation
HVAC Systems - Automatic
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.
A/C Mode
The vehicle operator can determine the temperature of the A/C air by using the temperature control. A 5-volt reference signal is sent out over the 5-volt
reference circuit to the air temperature actuator. When a desired temperature setting is selected, a variable resistor is used to determine the air
temperature door position 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 module uses this signal voltage to determine the air temperature actuator position
through the air temperature door position signal circuit. The motor opens the air mixture door to a position to divert sufficient air past the evaporator to
achieve the desired vehicle temperature. Warm heater air is mixed with cool A/C air at the air mixture door. When the coldest temperature setting is
selected, a 5-volt reference signal is sent and no warm heater air is mixed with the cool A/C air.
