How to test Blower Motor Resistor ??
 

Does anyone know how to test a blower motor resistor? My blower only works on high, so I pulled the resistor and checked it with my voltmeter.

My truck is an '82 F-100 and the resistor has a three connectors then one single connector. Using my voltmeter, 2 of the 3 connectors show continiuity with zero resistance when I used the single connector as the other point. The other one (of the 3) also showed continiuity, but at a higher resistance.

I know a bad resistor can cause the fan to only operate on high, but before I replace the resistor, I want to make sure that is the problem.

Any experience out there? Does anyone know if NAPA, or other parts place carry this resistor?

Thanks, Steve

How to test Blower Motor Resistor ??
 

You need an ohmmeter with a good low-resistance range to measure the actual values. Those resistors have values around a few tenths of an ohm. If you are reading continuity at each end of each "coil" they are almost certainly OK. Of course if there is a burned area and the ends are just barely touching all bets are off, but you could see that easily.

The other two-lead widget is a thermal fuse which opens if the resistors get overheated (for example, if a mouse nest in the heater box catches fire. Don't ask how I know). If it's open I believe you will not get any fan including high.

My Ford dealer has them for my '84 F150, for $23. Pep Boys, etc. did not.

How to test Blower Motor Resistor ??
 

How to test Blower Motor Resistor ??
 

Thanks Charles,

Got it up and working, it was the resistor. Thanks to your info I was able to pick out one at a junk yard. It does appear that the thermal fuse had blown on my old one. I was able to test the junkyard's resistor and the old coils all had low resistance (less than 2 ohms).

I called my dealer and they wanted $50 for one and it was not returnable on top of that. The junkyard resistor cost me 5 bucks plus the time it took to pull it out!

Once again Thanks, Steve

Oo.