My '86 has a heater fan but it only works on the high position. Do I need a new blower or a new switch? If a switch, is it easy to install or is there a thread for that?

thanks,

rustyford

 

You probably need a new resistor assembly. Go out and look in the ductwork, you should see a square thing with several wires going to it mounted in the duct. Take it out and it will look like a bunch of springs. See if any of them are burnt out.

Here's what it looks like.

 

Welcome to the forum, rustyfordhibbard!

My experience has been that the resistors burn out due to the blower motor either going bad or being under a heavy electrical load due to the fan/blower running against leaves or other debris that has made its way into the duct work. Has the fan ever made a screeching noise?

It is always a good idea to annually remove the blower assembly [located next to the resistor] and clean out the duct work. There have been dash fires caused by the hot resistor igniting dried leaves.

By the way, the resistor is located in the duct work so that the moving air helps cool the wire coils. The fan high speed bypasses the resistors.

 

X 2 on cleaning out the duct work. I bought a cab in NC that had a little fire from the collection of pine needles.

 

Thanks for the replies guys! This ductwork is in the cab of the truck, yes? Because I have the fan out and don't see anything like the pictures under the hood. I'll look there in the meantime.

 

Perhaps your system is a dealer installed one? Mine, with the blower under the hood on the passenger side, was equipped with A/C from the factory.

 

The resistor block is screwed into the plastic plenum under the hood.
The wire coils are inside the plenum with the harness connector facing out.
Most often it is not the coil that burns through, but the little thermal fuse. (Otherwise you would only lose *one* of the intermediate speeds)
I actually replaced my fuse for $0.69 a week or two ago.