Heater Blower Controls Circuit Description. Pontiac Sun Runner - 4WD (Canada) 1998

For 1990-2009 cars

The blower speed selector switch receives battery voltage through the heater fuse, 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. Because 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, the current passes only partially through the blower motor 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. The 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 the full current passes directly to the blower motor,