K 2500 Truck 4WD V8-305 5.0L VIN M SFI (1998)
Control Module HVAC: Description and Operation
The blower switch provides a choice of four blower speeds and OFF. It receives power through the HTR-A/C FUSE when the ignition is ON. In the LO
position, the circuit continues through the heater wiring harness to two resistors in the resistor assembly near the blower motor.
When the blower switch is in a medium-speed position, the circuit continues through the heater wiring harness to the resistor assembly, but it bypasses
one of the two resistors. When the blower switch is in the HIGH position, the circuit continues through the heater wiring harness to the resistor assembly,
but it bypasses both resistors to provide full power to the blower motor.
From the resistor assembly, the circuit goes to the blower motor terminal to operate the blower motor. The blower motor circuit is completed to ground
by a sheet metal ground wire that connects to a ground terminal on the cowl.
