TrailBlazer 4WD L6-4.2L VIN S (2002)
Control Module HVAC: Description and Operation
BLOWER MOTOR CONTROL PROCESSOR
The blower motor control processor controls the speed of the blower motor by increasing or decreasing the voltage drop on the ground side of the blower
motor. The HVAC control module provides a low side pulse width modulated signal to the blower motor control processor over the blower motor speed
control circuit. As the requested blower speed increases, the HVAC control module increases the amount of time that the speed signal is modulated to
ground. As the requested blower speed decreases, the HVAC control module decreases the amount of time that the signal is modulated to ground.