Thread: AC / Heater Blower Fan only works on one speed.

no its not part of the blower. it just happens to be right next to it squeezed up against the firewall. as long as you dont have the automatic temperature control the resistor is like 30 bucks at autozone.

Regardless of manual or auto temp, they both have resistors. The speed control is little more than a 12V source with four speeds. 12V/full current is full speed, and then three progressively higher resistance circuits @ lower current resulting in slower fan speeds.

You can tell you have a bad resistor when only the high speed works as this is the only circuit unaffected by its presence.

The resistors are kind of a wear item as they're basically electrical ballasts - they take current meant for the blower motor and bleed it off as heat. These heat cycles will eventually kill the resistor and open its circuit.