I have a 1999 4.2 L F150 which has a HVAC fan which blows air in only the two highest speed settings. The two lower speed settings do not work at all in both the heating and A/C settings. Can anyone provide any advise as to what the source of the problem is and if the repair will be costly?

 

Check for a faulty speed switch, resistor pack, or burned connectors on either.

Won't be anything else.

Steve

 

more than likely the resistor

 

Normal failure mode for the resistor is to only have HIGH speed. It's kind of unusual to loose two speeds as that would require that there be failures at TWO points at the same time.

Steve

 

Wow. I just did a search for this forum to find out THIS EXACT problem! My fan only works in the highest speed. Where is the resistor, what does it look like, and how do I replace it?
Thanks a ton in advance.

 

Never mind... figured it out. For those who are interested, it is located on the bottom of the fan housing in the passenger footwell. It is simply a circuit board held in place with two screws, and it has an electrical connector with 4 wires plugged into it.

I removed it, and sure enough, the resistors were all rusted out and falling apart. Hopefully this can be of some help to someone!

 

Did you replace just the two resistors, or the whole block of resistors? Is it even feasible to replace just the two resistors? How much was this fix for you (time/money)?

 

The resisitors come as a block. YOu cannot get individual components

First time you see them, you'll wonder why they look like a bunch of heater coils.... just various lengths of wire.

Steve

 

Here's some pics I posted a while back of this very thing. Hope they help as well.... -Mark B

https://www.f150online.com/galleries...w.cfm?num=9470