Monte Carlo V6-3.8L SC VIN 1 (2004)
Air Door Actuator / Motor: Description and Operation
MODE/RECIRCULATION ACTUATOR
The Buehler actuator is a 2 wire bi-directional electric motor. Two control circuits enable the actuator to operate. The control circuits use either a 0 or
12-volt value to co-ordinate the actuator movement. When the actuator is at rest, both control circuits have a value of 0 volts. In order to move the
actuator, the HVAC control module grounds the appropriate control circuit for the commanded direction. The HVAC control module reverses the
polarity of the control circuits to move the actuator in the opposite direction.
The HVAC control module determines the door position by counting motor pulses on one of the control circuits. These pulses are small voltage
fluctuations that occur when the brush is shorted across 2 commutator contacts as the motor rotates. As the actuator shaft rotates, the HVAC control
module monitors the voltage drop across an internal resistance to detect the pulses. The HVAC control module converts the pulses to counts with a range
of 0 to 255 counts. The HVAC control module uses a range of 0-255 counts to index the actuator position.
