Electrical Issues '94 Jeep Cherokee

[JeepFreak]

Been having a problem with my Cherokee Sport for some time now although I had remedied the problem a while ago. It finally came back. So what's been going on is that a few months back, my heater resistor went out and only the low setting would work on anything (heater, vent, defroster, A/C) but when you put it on the low setting it would work and the resistor would glow like crazy so I replaced it along with the 25 fuse (the old one was a blown out/melted 20 Amp because somebody put it in when it was supposed to be a 25 Amp). The new resistor worked great from a junked Cherokee from Pick n Pull. Just today as I was driving to pick up my wife, I kicked the A/C from High to Low (it hasn't been put in low since I installed the junked resistor and has worked fine without blowing the fuse) and all of a sudden my headlights dimmed, the car lost some of its power and the blower controls ALL stopped working except Vent which would work on High as if it was in Low. Other than that nothing works AND it blew the fuse which I just replaced about an hour after the issue happened again (I don't want to drive without a working fuse in). I am quite sure without pulling the resistor again that it is blown and done for. So my question is, is the old Pick n Pull junked resistor finally at the end of its life or is there possibly a short in the low setting since that seems to be where the problem originates? Any and all help would be appreciated!!! It's supposed to be in the 100's in Oroville!

[Mudderoy]

Been having a problem with my Cherokee Sport for some time now although I had remedied the problem a while ago. It finally came back. So what's been going on is that a few months back, my heater resistor went out and only the low setting would work on anything (heater, vent, defroster, A/C) but when you put it on the low setting it would work and the resistor would glow like crazy so I replaced it along with the 25 fuse (the old one was a blown out/melted 20 Amp because somebody put it in when it was supposed to be a 25 Amp). The new resistor worked great from a junked Cherokee from Pick n Pull. Just today as I was driving to pick up my wife, I kicked the A/C from High to Low (it hasn't been put in low since I installed the junked resistor and has worked fine without blowing the fuse) and all of a sudden my headlights dimmed, the car lost some of its power and the blower controls ALL stopped working except Vent which would work on High as if it was in Low. Other than that nothing works AND it blew the fuse which I just replaced about an hour after the issue happened again (I don't want to drive without a working fuse in). I am quite sure without pulling the resistor again that it is blown and done for. So my question is, is the old Pick n Pull junked resistor finally at the end of its life or is there possibly a short in the low setting since that seems to be where the problem originates? Any and all help would be appreciated!!! It's supposed to be in the 100's in Oroville!

My guess would be that you have a problem with the Jeep that is causing the problem, but lets see what the others here have to offer.

[slvmart]

You may actually be having a blower motor problem that is causing a higher than normal load on the resistor.

[4.3LXJ]

I think you may have a blower motor problem coupled with using old resistors. My opinion is that since these things fail anyway, using an old failure prone part just compounds the problem. One thing to make sure of is that the connections are all good. But it also sounds like you might have something else going on since the lights dimmed. Might check that alternator for output too

[bigmike441]

check your grounds for excessive corrosion, back probe with a DMM and see how many watts the blower motor is pulling

[JeepFreak]

Ok well I never thought it might actually be the blower motor itself. If I were to check how much power it was pulling, where would I go about probing to check? It did the same dimming of the lights the first time it happened so I think that's because it overloaded the fuse and blew it. And if it is the blower motor, would replacing the motor itself fix the problem or would I still need to figure out how it's causing the overload? It seems to only overload in the low setting which now that I think about it, does seem to possibly indicate a problem with the motor. Does anyone have an idea of where I can get a blower motor and resistor cheap and if so how much do they cost and are the motors easy to install?

[bigmike441]

locate the power supply going into the motor, get a T pin or some kind of needle you can put in the back of the plug without having to unplug it, turn it on, have ur DMM on volts dc, find a good ground touch one end to the T pin. it could be the coils inside the motor might have came loose and be touching another one diverting the power where it shouldnt go

[JeepFreak]

Ok and if it is the blower motor overloading the electrical system (seems pretty likely at the moment) installing a brand new motor, resistor and fuse should fix it right? If the part that's malfunctioning was to be replaced with a brand new working part I would assume that would remedy the problem or am I wrong?

[4.3LXJ]

I would like to test stuff to see how much it is pulling, but yes. New parts should fix it. One more thing, the connection on the fan switch and ballast resistor is important. It that plug is getting cooked, that will be part of the problem too.

[bigmike441]

you can check the resister with a DMM set to ohms there should be 4, one very small then it should step up with each one but if it works on all settings low medium and high then the resister is fine. but you should replace the fuse with the original amp it called for after you replace the blower motor if you decide to

[JeepFreak]

Ok and that might be a little bit of the problem too because the first time this happened there was a smallest form of smoke that puffed out of the climate controls for a fraction of a second. I was thinking it had arced but I never really got around to checking. I'm new to the electrical side of my jeep whereas the mechanical stuff I'm pretty good at. I know where and how to get to the resistor and I think I know how to get to the blower motor since I know what it looks like and I've seen it in my Jeep. The question is how to remove it and how to check all the other stuff. Do you happen to have or know where to get a diagram or video of the installation and removal of the blower motor and perhaps the way to go about checking specific things such as the fan switch and ballast since I have never looked at those before?

[bigmike441]

check youtube im sure its on there some where, as for the control unit u might want to get another one from the junk yard just to be on the safe side. this is what i found at just a quick look you can look harder, How To Remove Blower Motor On 1985 Jeep Cherokee - YouTube

[JeepFreak]

Ok I would assume that it probably isn't looking so good behind the climate controls. I'll check the Chico Pick n Pull for a climate system similar or the same as mine. They have a few good looking jeeps there (RIP). Thanks for the video. I'll get right on it.

[bigmike441]

no problem, let me know how it goes, i got a buddy who does alot of jeep work i can talk to him if that doesnt work