Heater switch only works on full high

[Doriansrjeep93]

So I have a 93 Cherokee and my switch for my heater blower only works when it's on high..... Don't work on any other settings but high. Vary baffling.

[4.3LXJ]

Dorian, there is a ballast resistor located on the blower housing under the glove compartment. It is what determines the motor speeds. They commonly burn up and need replacement. They are not expensive

[Doriansrjeep93]

Thanks for the vary awesome news. I was fighting with the air not being hot at all. Found out JackAs at midis when they replaced the water pump and thermostat,they never put back in a thermostat so my cooling system was always running cold. This is why I work on my own car. Told the guy I got it from to never go there again. Now it runs heater runs hot but the motor has one speed.

[bluedragon436]

The fear of stuff like that happening is part of the reason I like to work on my own vehicles when I can help it, that and the cost savings and knowing more about your vehicle and it's workings... I was just about to say to swap out the resistor, but as usual Steve beat me to it.. I'd almost think for sure that would remedy your issue... On a good note, at least you do have heat again, even if it is eye drying full blast heat!! LOL

[Pookapotamus]

Yup definitely the heater resistor, but I'm going to add to it a bit, the reason the resistor blows is that the blower motor is wearing out and the resistance is causing the heater resister to heat up and blow. It's a good idea to replace the blower motor at the same time as the resistor. And they are not that expensive.

Good luck!

[prerunner1982]

I had the same problem and just hadn't gotten around to replacing the resistor pack yet..... now it won't even work on high. haha..

[oderdene]

Pull out resistor pack and replace thermal fuse.

Resistor pack is visible under glove box

http://i85.photobucket.com/albums/k48/blackbeast1/blower%20motor/IMG_2028.jpg

factory thermal fuse is around 130 °C, you can source from radioshack, like this one http://www.radioshack.com/288af-140ac-thermal-protector-fuse/2701320.html#start=11

mine blown once during soldering, better to wrap around post tightly.

http://i519.photobucket.com/albums/u354/khinks01-02/HVAC/ResistorBlockThermalFuse128C2624FFuse-1.jpg

[Doriansrjeep93]

Cool I like the pics you took it will help me alot when I go to either pull one from the junk yard or to the parts store. Are junk yard here in SO has enough jeeps and parts you can put 5 or 6 together. Its where I'm going to pull my spare block from. Want to have a spare engine in case I go blow this one up.

[editedforsafety]

You might as well go with a new one. They tend to live a hard life so if you pull one from a JY chances are you are going to replace it soon anyway.

This one is from my dad's 2003 F150. The one in my 99 XJ was way worse.

https://mail.google.com/mail/u/0/?ui=2&ik=76b3dff92c&view=fimg&th=149cab41752d4aea&attid=0.1&disp=inline&realattid=1485250261380235264-local0&safe=1&attbid=ANGjdJ8aRonWddVPYqvW9SXkur2HkUeiMOONZD3BogD 2N3pFddHRNCPLbklbI8NujnnkhIC7-Z54CfFGL37vFl3dguuzaH5cnxwST-H8MuQ2WMpNSxPlMcerHdxo4l8&ats=1416445067580&rm=149cab41752d4aea&zw&sz=w1886-h800

[autotech98]

Had the same problem got the resistor pack from napa like $17.five minute fix

[Doriansrjeep93]

So got a new one and it works like a charm. The heat coming out its warm but it's not hot. So I think my heater core is going out or something like that. :-/ well just another part to be replaced next, good side of it is I get to work on my XJ and not have to worry about replacing it for some time. :D

[bluedragon436]

Glad to hear that it is all working out well... I would say try flushing and reverse flushing the heater core before you give up on it... and if nothing else it should give you more time with some good quality heat... I flushed mine using my air hose from my compressor... put some water in it, then flushed it again back and forth that way a few times... then after it was blown out I put some CLR in it and let that set for roughly 15 minutes... then blew it out in reverse... and then flushed with water again a few times... and it helped with my 98 quite a bit...

[Doriansrjeep93]

Good idea. I'm going to try it when I get my new air compressor on Sunday. Would make since on it getting clogged so I'm hoping I won't have to flush it with some harsh chems to remove any stuck on build up. :-/ but with all the stuff I've had to fix or replace I'm not pitting my eggs in a basket yet!!!! I've found this much in less then 2 months so i know there is going to be more to come. And thank you all again for the advice and tips. Keep them coming fellow XJer's. Maybe I can help on something of yours?

[ShadySpot46]

Good idea. I'm going to try it when I get my new air compressor on Sunday. Would make since on it getting clogged so I'm hoping I won't have to flush it with some harsh chems to remove any stuck on build up. :-/ but with all the stuff I've had to fix or replace I'm not pitting my eggs in a basket yet!!!! I've found this much in less then 2 months so i know there is going to be more to come. And thank you all again for the advice and tips. Keep them coming fellow XJer's. Maybe I can help on something of yours?

Good thread, and good to see that the problem was fixed.

You may already have this info, but in a search for manuals on my 2000 XJ, I ran across this site. Think the site is "inactive", but still has some reference manuals for XJs on it to download. They may eventually be taken down/site fully deactivated.

Just ignore the login screen and click on the Reference Documents:

URL is http://www.xjjeeps.com/

[nickxj94]

My 94 only works on high, my switch is getting to hot and melts the plug in, that resistor cause that? I've replaced the blower motor,and another heater switch and now it's burned up and only works on high.

[4.3LXJ]

Hey Nicky, the secret here is to use excess tinfoil from the hat, if there is such a thing :D

Actually that is not too far off. There is a lot of current going through that switch and if there is a somewhat loose connection there or or the switch is getting pitted inside it will generate heat and the more heat, the worse it gets until it fails. You will need a new switch and probably have to make a new connector for it. Use the yellow spade connectors that are supposed to be rated for 50 amps. I had to do this on an 85 i had that did the same thing