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Heater blower resistor keeps burning out

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  • Heater blower resistor keeps burning out

    OK, this is driving me nuts. I've replaced the heater blower motor resistor in my '86 grand wagoneer twice now. Each time, the heater will blow nice and hot for about three days, then I'll start up the jeep and nothing. The fan won't work.

    After the first replacement resistor went dead I thought maybe the problem was a buildup of debris around the heater core or something. So I cleaned all that out, disassembled, cleaned, and reassembled the blower motor and fan, then put everything back with a "new" resistor. (I used my A/C resistor this time).

    Started up the jeep and the heater came on just fine. Again, it worked for about three days and then this morning when I started it up, nothing.

    I have no clue what could be causing this unless I just got a string of bad resistors, which seems a stretch. Help!
    1986 Grand Wagoneer - Mostly Stock - Well-used

  • #2
    when it "burns out" is the fan dead on all speeds?
    If so, I'm guessing it's the thermal fuse on the resistor that's "blowing".
    If it is the thermal fuse that's blowing, you can buy just the thermal fuse at radio shack, I think when I got mine, it was around $2. I'll see if I can dig up a part number.

    The thing is, the thermal fuse needs to be crimped in place. If you try to solder it in, the heat from soldering will blow the fuse.


    Now, sense the thermal fuse blows when it gets to hot, you need to figure out what's causing the high temps. It could be electrical load(short or dragging blower motor), or wile this is less likely, if the temperatures inside the heater box get to high, that could also cause the thermal fuse to blow.

    EDIT: found the part number for the thermal fuse, NTE8149 It's listed as "web only" on the radio shack site, but I was able to find one at my local store.
    Last edited by muddy; 11-20-2012, 09:42 AM.
    1987 Grand Wagoneer,
    well worn, bone stock, with 120K miles.
    added a snow plow, and looking for a lift.

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    • #3
      Originally posted by muddy
      when it "burns out" is the fan dead on all speeds?
      If so, I'm guessing it's the thermal fuse on the resistor that's "blowing".
      If it is the thermal fuse that's blowing, you can buy just the thermal fuse at radio shack, I think when I got mine, it was around $2. I'll see if I can dig up a part number.

      The thing is, the thermal fuse needs to be crimped in place. If you try to solder it in, the heat from soldering will blow the fuse.


      Now, sense the thermal fuse blows when it gets to hot, you need to figure out what's causing the high temps. It could be electrical load(short or dragging blower motor), or wile this is less likely, if the temperatures inside the heater box get to high, that could also cause the thermal fuse to blow.

      EDIT: found the part number for the thermal fuse, NTE8149 It's listed as "web only" on the radio shack site, but I was able to find one at my local store.
      Thanks, muddy. I'll swing by radio shack and see what they've got. I'm guessing my problem is a short somewhere since I've never had it stop working on me while driving. It will stop working over night, every time. Very strange.
      1986 Grand Wagoneer - Mostly Stock - Well-used

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