Control Module HVAC: Description and Operation

The blower motor is controlled by a four-position heater blower motor switch located on the left side of the control assembly. The four positions are LOW, MEDIUM LOW, MEDIUM HIGH and HIGH. The four operating speeds are obtained with a heater blower motor switch resistor connected in series with the heater blower motor switch operating on the ground side of the blower motor.

With the function control knob in the OFF position, the blower motor will not operate.

With the heater blower motor switch at LOW, current flow in the ground circuit is through three resistors to obtain the lowest operating speed.

With the heater blower motor switch at MEDIUM LOW, current flow in the ground circuit is through two resistors to obtain a medium low operating speed.

With the heater blower motor switch at MEDIUM HIGH, current flow in the ground circuit is through one resistor to obtain a medium high operating speed.

With the heater blower motor switch at HIGH, current flow in the ground circuit by-passes the heater blower motor switch resistor to obtain the maximum operating speed.