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?
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.
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!