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Heater Problems


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I don't understand what or why it is happening, but in my 1991 MJ there is always heat coming out of my top vents, contently. i though oh well i'll just unplug my heater and take care of it later.. well even after it was unplugged.. warm are starts blowing. and i have noticed that when i am at high speeds like freeway it is worse and blowing more air.. sooo yeah.. any idea's...

:idea:

 

little story... i got my windows tinted 3 hrs before my prom last Saturday... and after they where done they told me i couldn't role my windows down for 3 days so the windows can dry out :doh: ... let me just say... it was hot in there.. and my GF and i started getting irritated... lol i need help!!! :fs1:

 

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Sounds like possibly two issues. A lack of vacuum to the control head, and a cable disconnected from the heater door. With no vacuum to the heater it defaults to defrost mode, but the temp (blend) door is cable controlled. So even with no vacuum you should have been able to slide it all the way to 'cold' and just had outside air coming in. Of course if it was hot out, and your engine was hot, it wouldn't have been 'cold'. I would check the vacuum lines going to the control (there are possibly ten posts about this so far this year). As for the temp door. Slide the knob all the way hot and all the way cold, with a bit of force. You should be able to hear the door thud as it closes both ways. If not, it may just need adjusting.

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The vacuum leak could be almost anywhere. One common failure point is at the vacuum reservoir located behind the front bumper on the passenger side. The lines running into it can get very brittle and crack.

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The vacuum leak could be almost anywhere. One common failure point is at the vacuum reservoir located behind the front bumper on the passenger side. The lines running into it can get very brittle and crack.

 

 

Welll i found that this was disconnected..i think... but it is still goinging... is that not even the right thing? :hmm:

 

rw5ohw.jpg

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that could be it. where is that located? Your pic is kinda dark

 

Looks like it might be an upside-down pic under the MJ. I think there is a CA in the lower left hand corner of the pic to orient yourself if that helps...

 

Rob L.

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Welll i found that this was disconnected..i think... but it is still goinging... is that not even the right thing? :hmm:

 

rw5ohw.jpg

 

That looks like a poor pic of the the vacuum line connector that plugs on the vacuum reservoir behind the right side front bumper. It also looks like the vacuum line connector that connects to the water control valve in your heater hoses. Like someone said - in what general area did you aim the camera to take this pic??

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Welll i found that this was disconnected..i think... but it is still goinging... is that not even the right thing? :hmm:

 

rw5ohw.jpg

 

That looks like a poor pic of the the vacuum line connector that plugs on the vacuum reservoir behind the right side front bumper. It also looks like the vacuum line connector that connects to the water control valve in your heater hoses. Like someone said - in what general area did you aim the camera to take this pic??

 

oh i'm sorry, yeah that is behind the front bumper, on the right side, where Pete said to look.

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where would that be, and what would it look like?

 

On your 91, it will be a black plastic blimp looking canister, black plastic, about 6" x 3", not a ball. It's tucked up directly under the right side front bumper next to the horn. To access it you have to pull down the splash shield if it's still there.

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  • 3 weeks later...
sbk2zn.jpg

 

 

is this the right one for my truck, i took it off a 1990 cherokee that i have...? :huh???:

Yeah that should work. Its not the exact one, and possible if you have cruse control your heater might go into defrost mode when you hit the pedal..

 

I do not have a vac res on my 96 XJ at all, and with cruse and it still blows out the dash unless I'm in cruse accelerating, then it only defaults until the truck is to speed..

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So i found this ball and everything odd my parts Cherokee and put it in.. but i can't find what all plugs into it... there is the one... but then nothing else... what am i missing?

 

 

 

2946wiu.jpg

 

 

and this is with the ball pullled out and the one connected to the ball still.

5ujyh2.jpg

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According to my parts manual, the 91s only came with the football-looking reservoir. My 91 had the football. These reservoirs have no built-in check valve. I think the ball-type reservoirs did. On the 91 and up, the check valve for the climate control is an inline device located on the vacuum line going thru the firewall to the HVAC controls as show in the pic below in the upper red circle area. If this check valve is missing and/or bad, the vacuum controlling the HVAC doesn't work properly or at all. Since these valves seldom go bad though, I think if you re-install the correct football reservoir and hook it up your problems will go away. :D

 

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