Heater stuck on defrost on my 98 grand cherokee - JeepForum.com
 
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post #1 of 9 Old 01-12-2013, 12:13 AM Thread Starter
MALL
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1998 ZJ 
 
Join Date: Jan 2013
Location: Cordova
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Heater stuck on defrost on my 98 grand cherokee

I am looking for a vacuum leak with no luck so far. Is there a known trouble spot to look at first?

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post #2 of 9 Old 01-12-2013, 12:16 AM
NewtoZJ
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I had a problem similar to this. I believe it was like the main vacuum line for the heater. I'd have to check my paperwork.
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post #3 of 9 Old 01-12-2013, 12:27 AM
SAR-Swimmer
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1997 ZJ 
 
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@ MALL, just a note, if you have a 98 Grand cherokee, it would be ZJ, not an XJ.
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post #4 of 9 Old 01-12-2013, 12:39 AM
zeejay92
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if its a 4.0, theres a vacuum line on the end (firewall side) of the intake manifold with a check valve, check that valve with the conditioning of the hoses is a good place to start
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post #5 of 9 Old 01-12-2013, 05:04 AM
KoreaZJ
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Quote:
Originally Posted by zeejay92 View Post
if its a 4.0, theres a vacuum line on the end (firewall side) of the intake manifold with a check valve, check that valve with the conditioning of the hoses is a good place to start
...then follow it from there. Tees off through the firewall near the PCM (runs to HVAC control panel), runs to cruise servo and vacuum reservoir (under battery tray.)
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post #6 of 9 Old 01-13-2013, 01:05 AM Thread Starter
MALL
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1998 ZJ 
 
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I found the leak

I have a disconnected vacuum hose at the fire wall...but it gets worse. The Vacuum line has dissapeared into the firewall. I have removed the entire dash and the line is still not exposed. It is still behind the heater core and I am not sure if I want to tear it out also. My question is, does the black vacuum line that goes through the fire wall go directly to the selector or does it attach to something else first? I am considering relocating and rerouting the vacuum line if that will work. Any thoughts?

Last edited by MALL; 01-14-2013 at 12:13 AM.
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post #7 of 9 Old 01-13-2013, 01:46 AM
Uniblurb
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On a 96 4.0, which should be about the same as a 98, the black vacuum line runs overtop of the HVAC box and there's a plastic clip on the seam of the box, about behind/under the left side of the glove box, then the black line goes directly left to the AC/heater control switch. It attaches to nothing else on mine and is the main vacuum feed for all the other vacuum lines attached to the back of the switch.

Good luck and you may want to try to fish around a little with a wire with a smallhook on the outside of the firewall to see if you can hook/retrieve the line from the hole. I lost mine in the hole once and it was about in the 7-8 o'clock position, didn't go far since tight up against the firewall, and finally grabbed it with a thin pair of needle-nose pliers.

2004 4.7L WJ Limited, 96 4.0 ZJ


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post #8 of 9 Old 01-13-2013, 04:08 AM
KoreaZJ
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Pulling the heater housing would be last on my list.

Black vacuum feed line runs from the firewall to a quick disconnect located (and clipped in) near the HVAC control panel...


After removing from the clip, the quick disconnect can be pulled out for access...


Entire harness looks like this, same part for all ZJ's I believe. Long black line runs to the firewall.


A new vacuum line can be easily spliced in before the quick disconnect... if you can snake one in from the firewall.
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post #9 of 9 Old 01-14-2013, 12:24 AM Thread Starter
MALL
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1998 ZJ 
 
Join Date: Jan 2013
Location: Cordova
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Thanks for the input, I will give it a shot tomorrow. With the dash out of the way it should be easy, but if I would have thought of this sooner it probably could have been accomplished by just removing the glove compartment.

Last edited by MALL; 01-14-2013 at 08:32 AM.
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