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Unread 11-08-2008, 03:51 AM   #1
hmmhoyhoy
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Heater only shoots heat out of the defrost vents

My heater was working great but now it only shoots heat out of the defrost vents. Nothing comes out of the floor or the vents on the dash. I have no idea whats going on. I can flip through every setting and it always shoots out of the defrost vents. Any ideas.

94 ZJ 5.2

Thanks guys

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Last edited by hmmhoyhoy; 11-08-2008 at 03:51 AM.. Reason: Reason
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Unread 11-08-2008, 04:26 AM   #2
10achik
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You have a disconnected or cracked vacuum hose under the hood, probably around the throttle body area. I'm betting your cruise control doesn't work either does it
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Unread 11-08-2008, 11:50 AM   #3
michiganmaveric
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Quote:
Originally Posted by 10achik View Post
You have a disconnected or cracked vacuum hose under the hood, probably around the throttle body area. I'm betting your cruise control doesn't work either does it

I second that opinion.
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Unread 11-08-2008, 06:19 PM   #4
ChiSilverSupra
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wow, i have that same problem. i'm gonna check it out tonight, all this time i thought that it was the selector.
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Unread 11-08-2008, 06:57 PM   #5
10achik
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2006 Saturn Redline -2.0L Eaton supercharged I4, GMPP Stage 2, Custom Tune, AEM CAI, Ebiach Pro Kit w/ swaybars, EVO Ventus V12s (13.76 @ 103.85)
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Unread 11-08-2008, 07:27 PM   #6
mdav8629
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One other place to check is look under the dash on the drivers side. If you look towards the glove box, there is a plastic white arm. It is right behind the message center. The lever breaks right by the eye that connects it to the shaft. If it is broken you will only get light defrost and heat. Just my 2 cents. Also there is an arm right under the ignition, try to push that up manually.
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Unread 11-09-2008, 04:08 PM   #7
hmmhoyhoy
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Quote:
Originally Posted by 10achik View Post
You have a disconnected or cracked vacuum hose under the hood, probably around the throttle body area. I'm betting your cruise control doesn't work either does it
Good call, my cruise doesnt work and it stopped around the same time. I will check it out thanks guys
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37" BFG AT's

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Unread 11-09-2008, 04:21 PM   #8
hmmhoyhoy
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Do you have an idea of exactly which hose could be cracked? I'm looking at it and everything looks fine, so I'm not sure where to start looking. Thanks
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37" BFG AT's

02 WJ Overland
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Unread 11-09-2008, 04:27 PM   #9
EagleStorm
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Could be your vacum source at the intake or by the vac canister. It defaults to defrost when there is a failure the fed's require it so alt least you can see out the windshield if there is a failure in your HVAC. ck the harness all the way from the manifold to the crusie and to the canister
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Unread 11-09-2008, 09:00 PM   #10
hmmhoyhoy
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Ok I have checked around for quite some time and am not finding anything broken or loose or cracked. I am not 100% sure what I am looking for though. Does anyone have anything specific as to what to look at, and a name for hose,vaccum line or whatever it may be?


Thanks for the help
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Dana 60 f with ARB 10.25 r and open. 5.13s
37" BFG AT's

02 WJ Overland
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Unread 11-09-2008, 09:07 PM   #11
magnumcherokee
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Follow your vacuum lines to where they end,your going to follow one to a black round ball. This is your vacuum reserve, so that when you are on the throttle and vacuum is low, you do not lose your heat setting. there is a second vacuum line out of that to your firewall and into your dash selector. One of these two plastic lines is leaking. If you pull the one from the intake to the black reserve at the reserve end, and check for vacuum while the engine is running. If you can feel it suck to your finger, that vacuum is present, that line is good move to looking at the other one. If not, replace it with vacuum hose or find where its broken and splice it together with a piece of vacuum hose that fits TIGHTLY over the plastic line.
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Unread 11-10-2008, 03:07 PM   #12
hmmhoyhoy
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Thanks I will check it out when I get home from work
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Dana 60 f with ARB 10.25 r and open. 5.13s
37" BFG AT's

02 WJ Overland
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Unread 01-25-2009, 02:36 PM   #13
94SportJeep
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TRY THIS
I had the same problem (Heat only blows throw Defrost setting), after checking everything, vacuum tubes, vent arms, switches, lines etc....
I finally randomly found the problem yesterday while doing an oil change. The vacuum line that runs under the hood located beside the battery. The line continues into the headlight bay. It was fully cracked just to the left of the battery. I replaced the broken portion of the line (1 inch) and everything works like new again.
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Unread 01-25-2009, 02:44 PM   #14
10achik
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Quote:
Originally Posted by 94SportJeep View Post
TRY THIS
I had the same problem (Heat only blows throw Defrost setting), after checking everything, vacuum tubes, vent arms, switches, lines etc....
I finally randomly found the problem yesterday while doing an oil change. The vacuum line that runs under the hood located beside the battery. The line continues into the headlight bay. It was fully cracked just to the left of the battery. I replaced the broken portion of the line (1 inch) and everything works like new again.
Thats the vacuum line that runs to the reservoir, it's kind of the "end of the road" for the system, that section you're talking about is probably from the battery leaking at some point and dripping down on the line. Then again it could just be old. Good find though
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99 GC Limited - 4.7L HO V8, 6.5" IRO HC LA lift, F&R D44s locked & trussed, 242HD, IRO TC Skid, KMA Bumper, 35's
2006 Saturn Redline -2.0L Eaton supercharged I4, GMPP Stage 2, Custom Tune, AEM CAI, Ebiach Pro Kit w/ swaybars, EVO Ventus V12s (13.76 @ 103.85)
2006 Pontiac G6 GTP
2012 Nissan Juke - (hers)
2000 SV650 - naked, integrated tail light, sliders, corbin, pilot roads, RK chain & sprokets, D&D full exhaust, FactoryPro Stage I jet kit, +4 Ignition Advancer, Barnett race clutch
2006 Triumph America 900 - Full Dresser

January 2009 Grand Cherokee of the Month (GCOTM)
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Unread 02-28-2009, 08:53 PM   #15
Bmoore89
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What does the cruise control have to do with the vacuum hose? I have both of these problems, but never thought that they could be related.

I'm pretty new to this whole Jeep/car repair thing, so dumbing it down would help.
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