HVAC Blower Controls Circuit Description. Pontiac Sun Runner - 2WD (Canada) 1998

For 1990-2009 cars

Battery voltage is applied through the heater fuse to the blower speed selector switch when the ignition switch is in the ON position. When the blower speed selector switch is turned to any position other than OFF, battery voltage is applied through the closed contacts in the blower speed selector switch.

When the blower speed selector switch is in the LOW position, current must travel the entire length of the resistive element in the blower motor resistor, to the blower motor. Since the blower motor is permanently grounded at G201, the blower motor runs at LOW speed.

When the blower speed selector switch is in the MEDIUM 1 position, current passes only partially through the blower resistor before reaching the blower motor. Because less of the blower motor resistor is a part of the circuit, the resistance in the circuit is lower, the current is higher, and the blower motor operates at a higher speed.

The MEDIUM 2 operation is identical to the MEDIUM 1 operation, except that even less of the blower motor resistor is in the circuit. Therefore, MEDIUM 2 operation is faster than the MEDIUM 1 operation.

When the blower speed selector switch is in the HIGH position, the blower motor resistor is bypassed and full current passes directly to the blower motor.