Heater fan works on high

I have a 2000 F150. The heater fan works on high but not on low or medium.
Someone at the dealership parts dept told my wife about three resistors that could be the problem. Anyone know where they are? Or know what the problem might be.

They are usually located on the heater/blower motor cover under the hood.Time and heat will cause them to fail.

Thank You
I'll check it out.

It is the resistors, I'm positive. The High setting doesn't need the resistors since the motor is being fed the highest possilbe amount of current. On the other settings, the extra current is fed through coils of wire to expend the the extra energy. There will be three small seperate coils in the resistor pack. The largest one is for speed 1, the next largest is for spead 2, etc, etc.

Resistors are an easy fix, expensive little buggers though considering their simple design. There should be two screws for a 'square' unit near your blower housing, unscrew them. The resistor set should pull right out. Disconnect the wire set leading from the resistor pack to the vehicle harness, disgard the old set. Plug in the new set to the harness, insert the new resistor set into the housing, screw the new set back into the motor housing.

Mice have destroyed two sets of mine. Now I have screened off my outside air intake grates so the little creeps can't get down into my blower/vent any more.

Note 1: Be careful not to damage the coils while handling/installing the new ones.
Note 2: You'll smell the 'new' metal burning the first few times you use the blower, don't be alarmed.
Note 3: If you always run your fan on high, it will burn out much much faster.

Thanks to all who responded. It was the resisitors. Was'nt very hard to change. I used a mechanics mirror to help me find it.


Thanks