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Unread 12-10-2013, 09:03 AM   #1
WranglingMI
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1998 TJ Wrangler 
 
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Heater Problem. Either on or off no inbetween

I have a 98 that has been running good since I bought her about 8 months ago. About two weeks ago all of a sudden the heater fan stopped blowing except on the highest level. Positions on the dial one, two, and three do not turn on the fan like they should, only the 4th dial (or 100%) will work.

Previously when it started getting cold and I was using the heater a lot I noticed a burning smell coming out of the vents, it smelled like burning electrical wire but it was entirely sporadic and only lasted 5 or so seconds on my 30 minutes commute. Also my alternator recently failed but I doubt that would have anything to do with it as I replaced that only a few days ago.

I was wondering if anyone else has had this problem and where I could start looking for a solution. Not sure if its a simple dial failure or the whole unit. Its about 10 degrees here in Michigan so I'm not using the lower settings obviously but if there are exposed wires in there, I'd like to get them repaired.



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Unread 12-10-2013, 09:12 AM   #2
JBTJ
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What happens is the blower motor starts to wear with age, thus pulling more current than the circuit can handle. Therefore, it starts to melt things as you have noticed. Your resistor pack located in the air plenum box just above the passenger foot well needs to be replaced. You may also want to pull out the control panel and inspect for signs of melting, which you may have. A temporary fix is to replace the blower motor, but a permanent fix would be to do the relay mod.
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Unread 12-10-2013, 09:22 AM   #3
WranglingMI
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If the circuit can't handle the higher current, why would it work on the highest draw and not the lowest? My apologies but I'm not sure what the relay mod is, could you link me?
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Unread 12-10-2013, 09:33 AM   #4
JBTJ
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Quote:
Originally Posted by USNTJ View Post
If the circuit can't handle the higher current, why would it work on the highest draw and not the lowest? My apologies but I'm not sure what the relay mod is, could you link me?
Because the resistor pack is fried and the current only goes to the highest setting. JEEP trying to save money thought it would be a good idea, but it wasn't, to have the speed switch control the blower motor. So when the blower motor pulls more current than the switch can handle then parts begin to fail. The relay mod inserts a relay between the switch and the blower motor relieving the added stress to the circuit. So what you have now with the relay mod is the switch controls the relay, which in turn controls the blower motor. You can use the search function and type in fried blower motor switch and read tons of info on the subject.

In the first 5 years of my JEEPs life, I replaced the speed, mode switches, and resistor pack several times. Did the relay mod and no more problems, and that was 7 years ago.
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Unread 12-10-2013, 09:39 AM   #5
WranglingMI
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Quote:
Originally Posted by JBTJ View Post
In the first 5 years of my JEEPs life, I replaced the speed, mode switches, and resistor pack several times. Did the relay mod and no more problems, and that was 7 years ago.
I will try this, thanks for the help.
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Unread 12-10-2013, 10:49 AM   #6
boykinjw
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Since it's getting cold if you need to be up and running fast the resistor pack is under $50 and can replaced in 15 min. You can then plan out the relay fix.
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