Question about blower motor resistor

Ive been told two things, and i need some clarification. My jeeps blower knob only works on the "High" setting.

Friend A said its the blower motor resistor, easy fix.

Friend B said its the blower motor resistor, which is blown because the blower motor is wearing out. More work and money to fix.

Can someone help me out here?

you should be fine with just the blower motor resistor.

Thanks.

I like Friend A better.

...but seriously folks, don't wanna be a hijacker, but my blower was working fine yesterday...today, not at all. Fuse good, any ideas? I'd need a Friend C.

lets go with technician B. been there done that. oe parts. blower and resistor. if you purchase a resistor then return to purchase a blower and another resistor they wont take back the one that burned up from the high current draw from the old motor. speaking from first hand experience. replace both.

your gonna be pissed listening to technician A. do it nice or do it twice. do you know the difference between half ass and whole ass? there is no difference. a whole ass is just 2 half asses put together.


para. check your switch assembley. they do burn up. lot of times from above. to be sure check voltage to motor. you can simply tap on the motor while its turned on. may fire right up.

You won't know whether you are "fine" until you change out the resistor and see how long the new one lasts. Something causes the resistor to fail. It may just be a one time glitch or it may be a failing motor causing a heavy current draw. The last time this happened on my 93, I "blew" two resistors (normally an easy repair with a new ~$1.50 thermal fuse if you want to go that route) before I replaced the motor which fixed the problem.

Replacing the blower motor on older models is very easy but I know that on later models, e.g. the 2000, you have to evacuate the A/C to move components to get at the blower motor. Review the threads listed at the bottom of this page -- one has the procedure for the 2000. I don't know if the 99 has the same setup.

cjkeeth said:

your gonna be pissed listening to technician A. do it nice or do it twice. do you know the difference between half ass and whole ass? there is no difference. a whole ass is just 2 half asses put together.

Click to expand...

I've never heard it put so eloquently but he is absolutely right... I've never had a resistor go out that didn't have to also have the blower motor changed. As these motors age they start to draw more current to turn the motor which eventually burns out the resistors. In this instance the resistor acted somewhat like a fuse which protected your wiring from the high current draw from the motor. While you can replace the resistor only, you will get a few weeks, maybe even a year but it will break again and you will be stuck putting a new blower motor in anyway. Might as well do it right the first time and not be stuck doing the same job over again soon. Also, given the pretty much universally crappy wiring that exists in these "Station Wagons..." (I always laugh when I type that) I personally wouldn't want to put any sort of unnecessary current load on the wires that supply the motor. :nono:

I agree with the other posters but should note that the same thing happened to my XJ less than a year after I bought it new. Sometimes they just go bad and the dealer explained that this is the spot where leaves and water tend to accumulate if they somehow sneak in. They simply changed the resistor pack and it still works perfectly. I would open it up first and look inside for debris. If it is clean, change the motor as well. If it has crap in it, clean it out (try to find the source) and go with the new resistor pack. You can pick one up in a junkyard for cheap.

I replaced mine, twice, two years apart. The blower motor in mine is fine. I'm not telling you that your's is though.

Each time mine burnt out it took out part of the harness, or maybe the harness melted and took out the resistor, who knows?

Here's my $0.02. Don't buy one used, don't buy one from a parts store. Spend a few bucks and get this part from the dealer. Both times I snipped the relevant setion of harness from a wrecked XJ and carefully took the plugs apart, then re-wrapped it. Don't use any splices, butt connectors, twist connectors etc! You can't add to the resistance in the curcuit (think hot spots) without causing more issues. Make sure the connections on the plug are shiny and clean. NAPA sells a contact cleaner/corrosion inhibitor for electrical connections, Use it. This isn't a hard fix, the difficult part is stuffing my 6'2" 285lb carcass under the dash and finding all the trim screws.

I have replaced 2 thermal fuses in the resistor pack(via radio shack),and was easy to do for a temp fix. I did this the first time only as a temp fix until I could get the funds for a new blower motor. My fuses popped a week later and by then I was able to buy a new motor and then replaced the thermal fuse the 2nd time(via radio shack). Oh and this was on a 93, 4.0l, aw4,4x4 sport.

On my 96 I was able to get a few years out of the first resistor I replaced with a Radio Shack one. Once that one died the next only lasted a month so I replaced the blower motor and resistor.

OK, option 4.....troubleshoot before blowing money on parts.

Does the motor work on the high setting? If not, it isn't the resistor.

That leaves the switch or the motor. Unplug the motor and jump +12v and ground to the motor (not a big deal about polarity). If the motor doesn't turn its the motor. If it does, you either have a bad switch, blown fuse, or bad wiring.

Per first post, motor works on high setting.

Unless the HO Jeeps have a different resistor pack than Renix jeeps (which I doubt) many posters here are confusing a resistor with a thermal fuse that physically looks like a diode that is part of the resistor pack, but it is not a resistor. The actual resistors are massive coiled wires, and they only go bad bad after very long exposure to water (condensate from the AC) and corrosives like maybe road salt up north (which I have heard rumors is taking its toll on later model HO jeep evaporators, and maybe the resistor connections as well, they are crimped,....and other vehicles of the same vintage that have aluminum evaporators, or leaks from an evaporator or heater core that leave corrosive salts behind on the resistor wires. Those resistor wires get red hot, and any organics that get on the resistor (like antifreeze, or refrigerants and oil) will decompose the organics forming organic acids!!!!!

That thermal fuse would fail from a locked up motor (I think) or from a blocked air flow (like an iced up condenser?) as the resistor wire would not have air passing over the wire to cool it and the thermal fuse would sense the dangerous temperatures and blow the thermal fuse.

X2 on Old mans post!

Also, you have no idea how old the blower motor is on a newly acquired, used jeep. It might be new already!!! So look at the history, and age of parts, actually pull the resistor pack (takes about 2 minutes), and the fan switch, takes 5-10 minutes, and look for loose burned, corroded signs of the problem.

Lastly, on the Renix jeeps (Did the OP ever tell what year his beast was????), the wire that goes from the fuse box, to the ignition switch to the fan switch and the resistor pack and motor, is way overloaded with other accessories on it like the radio, the WSWipers, the electric door locks and electric windows etc, and the failure problem is frequently compounded with poor, old dirty previously overheated contacts at the fuse box and the ignition switch. I had to bypass both fuse box and ignition switch and run new wire and new fuse holder on my 87 and 85. That was over 5 years ago now.