Blower Motor: Description and Operation

How the Climate Control Circuit Works

Blower Controls

The fan speed is automatically controlled in the fully-automatic mode. You can manually select the fan speed by turning the fan control dial clockwise, just past the AUTO position. This takes the fan from automatic mode to its lowest manually controlled speed. Turning the dial further clockwise increases the fan's speed, which increases air flow.

Battery voltage is applied through fuse 56 to the blower motor relay contacts at all times. With the ignition switch ON (II), the blower motor relay in the under-hood fuse/relay box is energized which feeds battery voltage to the blower motor. The blower power transistor controls the blower motor in all speeds except HIGH. The blower power transistor is controlled by the climate control unit. When the control unit requests HIGH blower speed, it grounds the blower motor HIGH relay coil, energizing the relay, which connects the blower motor directly to ground, making the blower run at high speed.

In cold weather, the blower will not come on automatically until the heater starts to produce warm air.