heater speeds

2000 f-150...heater/ac only works on high.The haynes manual leads me to believe that the thermal limiter is defective. I cannot find it as they describe in their book. Any help would be appreciated!

Other than a defective blower control switch what else would cause this?

Any other ideas!

Thanks

It is the resistor network, hands down....

Lay on your back and look up in the passenger's floorboard. The network is next to the blower motor itself. If it isn't working on the others, when you pull it out, you will probably find a burnt spot on it. The side you can see in the floorboard is only a connector. It is brownish junkboard type color and somewhere around 3 or 4 inches long and an inch or 2 wide.

Jyount...thank you!

I found the board exactly where you said it would be. It had a burn mark as you said it would and was so corroded that some of it crumbled right in my hand.
You called that one...thanks again!

Thanks for the update, and you are welcome! That is the only reason I hang around these sites, I have a desire to help others.