K 1500 Truck 4WD V8-4.8L VIN V (2003)
Air Door Actuator / Motor: Description and Operation
HVAC System - Manual
AIR DELIVERY
Mode Actuator
The mode actuator is a 5-wire bi-directional electric motor that incorporates a feedback potentiometer. Ignition 3 voltage, low reference, control,
5-volt reference and position signal circuits enable the actuator to operate. The control circuit uses either a 0, 2.5 or 5-volt signal to command the
actuator movement. When the actuator is at rest, the control circuit value is 2.5 volts. A 0 or 5-volt control signal commands the actuator movement in
opposite directions. When the actuator shaft rotates, the potentiometer's adjustable contact changes the door position signal between 0-5 volts.
The HVAC control module uses a range of 0-255 counts to index the actuator position. The door position signal voltage is converted to a 0-255 count
range. When the module sets a commanded, or targeted value, the control signal is changed to either 0 or 5 volts depending upon the direction that the
actuator needs to rotate to reach the commanded value. As the actuator shaft rotates the changing position signal is sent to the module. Once the
position signal and the commanded value are the same, the module changes the control signal to 2.5 volts.
Recirculation Operation
Recirculation Actuator
The HVAC control module controls the air intake through the recirculation actuator. Recirculation is not available when the mode is in defrost. When
the mode is in defog, Recirculation will only be available for 10 minutes. The operator must activate the blower for Recirculation operation. The A/C
high-pressure recirculation switch can cause the HVAC system to recirculate air. If the recirculation switch is pressed into the ON position when the
mode switch is in an unavailable mode position, then the recirculation switch LED will flash 3 times. When the high side pressure reaches 2206-2620
Kpa (320-380 psi), the PCM will place the HVAC system in recirculation mode. The high side pressure is lowered when the inside air cools the
refrigerant within the NC evaporator. When the high-side pressure reaches 1447-1861 Kpa (210-270 psi), the PCM will place the HVAC system out
of recirculation mode.
AIR TEMPERATURE
Air Temperature Actuator
The air temperature actuators are a 5-wire bi-directional electric motor that incorporates a feedback potentiometer. Ignition 3 voltage, low reference,
control, 5-volt reference and position signal circuits enable the actuator to operate. The control circuit uses either a 0, 2.5 or 5 volt signal to command
the actuator movement. When the actuator is at rest, the control circuit value is 2.5 volts. A 0 or 5 volt control signal commands the actuator
movement in opposite directions. When the actuator shaft rotates, the potentiometer's adjustable contact changes the door position signal between 0-5
volts.
The HVAC control module uses a range of 0-255 counts to index the actuator position. The door position signal voltage is converted to a 0-255 count
range. When the module sets a commanded, or targeted, value, the control signal is changed to either 0 or 5 volts depending upon the direction that
the actuator needs to rotate to reach the commanded value. As the actuator shaft rotates the changing position signal is sent to the module. Once the
position signal and the commanded value are the same, the module changes the control signal to 2.5 volts.
