mcfadyen72

95 Cherokee Sport, 4.0L.
My heater started to cut out. first i just pushed on the face of the control unit and it would start again.
i pulled the dash plate off and the stereo out and wiggled the wires on the back of the unit and it would start then cut out.
when i touched the top of the unit in the middle it's freaking hot! like you can't hold your finger on it for more than 3 seconds without seriously burning yourself.
any ideas? is the whole unit bad? i don't have much electrical testing stuff other than a basic test light.

mcfadyen72

anyone? anyone? buhler?

caged

i have been fighting that same problem in my tj for the last 4 years also.
i have replaced the hvac control unit, but now this one is doing it too.

jp magazine did a write up a couple years back about wiring up relays for each speed setting, as they overheat and tend to burn up possibly creating a dash fire.

does yours have the round contols, or the slider type?
i've had no problems with my xj slide controls however.

al2ride

Hot means drawinig too much current, check for flow obstructions...sometimes the black mesh filter thing breaks up and gets everywhere. Also check your blower motor...could be drawing too much current due to wear and tear.

mcfadyen72

whats the black mesh filter thing?

mcfadyen72

Actually i do recall hearing the blower motor making some weird noises a month back, but it hasn't done it for awhile.

BUT, why would the heater cut in and out when i jiggle the cables back there?

caged

on my tj, it's the wire harness that melts up, if i reach in through the glove box opening, i can grab the harness and wiggle it and it will kick back in.

mcfadyen72

dam, if its the cables melting, then you think i should take a new heater unit out of the junkyard but cut the connecters and wire and take them with, then splice it into my harness?

mcfadyen72

its the slider controls

mcfadyen72

>update<
i have replaced the hvac unit and it is still doing it. if i jiggle the wires it still does it, cutting in and out. i will have to splice in some new wires and connector i think.

also i got a new blower motor from a junkyard but it doesn't bolt in at the same points, i got it from a 92 so it should fit, but it doesn't.

what a gong show.

any ideas out there?

redmuck

are u touching the heater fan control switch? is that super hot? if it is, go buy a new one at the autoparts store. with the stereo out, u can change the switch with the right tools. unscrew the whole heater control,so you can pull it out a couple of inches,then take the wire harness off the fan switch, try not to break those clip things holding it on,like i did, i broke one side. if u hav one of those real small ratchets for tight places with a small bit socket, u can get the screws out.

mcfadyen72

no. i am touching the middle of the hvac control on the top. it is a new unit too. it seems to be the wires. im more pissed about the heater motor i bought and the mounting points are different. the control problem seems to be a short in the wiring harness.

semperfi

I have the same problem with my 94 XJ, other than knowing if it gets too freaking hot. 2 years ago, I had replaced the 4 position blower switch seeing that the factory connection was somewhat melted and the switch was seizing up. I broke off the factory connections and placed connectors on each wire. Again my heater is not working so I pulled the air conditioner/heater control panel out and I see that two of the 4 wire connections (yellow/tan and green wires)have toasted their connections on the wire and on the switch lugs.

I replaced the 4 pos switch and cleaned the connections. It works off and on. Sometimes I can hit the front of the dash and it would work. When it works all 4 fan speeds operate. Sometimes when it shuts off beating doesn't work but if I cycle the slide lever to the "Off" position and slide it to "Heat" or "Defrost" it will come on again. It may work 1 minute to 30+ minutes. Other times the beating and cycling doesn't work.

I can reach into the blower motor and spin the squirrel cage with my finger, so I guess the motor isn't binding. I looked at the outside portion of the resistor, it appears clean and assuming the other posters with resistor problems, mine works all 4 speeds.

I see according to the Hayne's electrical diagram the a/c heater panel also is a "switch". Could this be the problem?
TIA

mcfadyen72

FIXED!
I took out the junkyard blower motor an replaced it with a brand new one.
Also, i recharged the AC so it doesn't have to cycle so much.

The difference in price between a junkyard blower and a new one was like 20 bucks. if any of you are considering buying a junkyard blower motor, DON'T! its not worth it.

my heater works fine now, the hvac unit doesn't get hot and it doesn't cut in and out anymore.

cornfed85

i had a similar problem in my 92 xj and i replaced the blower motor and resistors and it works like a champ now...glad to see you got that jeep fixed and no more chance of a fire