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Unread 05-16-2012, 10:35 PM   #1
idahospudjeep
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1995 ZJ 
 
Join Date: Apr 2012
Location: Nampa, ID
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A/C blows through the Defroster

HELP! Its getting hot in Idaho and when my 95 Jeep Grand Cherokee Laredo 4.0 is at just an idol it will blow correctly out of the vents but when you start to drive it and foot on the gas it blows out of the defroster. Its cold air. (no matter what setting I'm at for the flow of air). Just would like to know if anyone else has had this problem and if anyone knows how to fix it or what is wrong. All the help the better....feel free to even e-mail me at shannon.egusquiza@yahoo.com

All Help Is Very WELCOME!

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Unread 05-16-2012, 10:59 PM   #2
Uniblurb
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Default for air circulation is out of the defroster when the main blend door isn't working correctly. Sounds like a bad actuator or vacuum leak. Look up right above the gas pedal under the dash and you will see the actuator with a piece of flat metal linkage going to the middle/underneath of the HVAC box to the main blend door. Make sure the vacuum hose isn't partially off or leaking.

Also in the engine compartment you will see a black vacuum line running across the firewall from the intake. There's a small black line which T's off which goes through the firewall which leads to your HVAC vent control switch. Also listen and look for vacuum lines here. This line also goes under the battery tray where the rubber hose can rot off causing not enough vacuum/leaks. You'll need to also listen to the dash for hissing vacuum leaks if you can't find any elsewhere. Good luck and let us know what you find.
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Unread 05-16-2012, 11:26 PM   #3
idahospudjeep
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We checked by the gas pedal and everything checks out there. In the engine compartment where the line goes under the battery we found that line to not be connected to anything and not rotten or any leaks at all. It just looks like it slipped off from some where and we don't have a clue where it goes. I will try to google some answers but if you know then that would be great also.

Thanks again.
your post was a big help.
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Unread 05-16-2012, 11:32 PM   #4
Oldfrog
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Mine does that occasionally when I accelerate. I let off the gas a little and it goes back to the vents. A Jeep tech once told me that he used to put a check valve in one of the vacuum lines to cure that issue. I've never fixed it, because it doesnt do it all the time.
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Unread 05-16-2012, 11:54 PM   #5
Uniblurb
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Quote:
Originally Posted by idahospudjeep View Post
We checked by the gas pedal and everything checks out there. In the engine compartment where the line goes under the battery we found that line to not be connected to anything and not rotten or any leaks at all. It just looks like it slipped off from some where and we don't have a clue where it goes. I will try to google some answers but if you know then that would be great also.

Thanks again.
your post was a big help.
YW. So is the vacuum line you found under the battery box just open with no plug or anything in it? If so that might be your problem. It should have a short rubber line, remove the battery tray, there's a plastic nipple on the very bottom of the tray, and plug it in. That may fix it if line is open and causing little vacuum getting to your HVAC circulation switch.
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Unread 05-17-2012, 12:13 AM   #6
jnicewan
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^ like he said, under the battery tray is a vacuum reservoir tank, its a small storage tank for vacuum pressure for when the engine is at heavy throttle (not producing vacuum). That vacuum line supplies the speed control and HVAC.
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Unread 05-17-2012, 01:02 AM   #7
idahospudjeep
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i found what you where talking about and connected it so i will find out if it works tomorrow thank for the advice.
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Unread 05-17-2012, 02:47 PM   #8
Uniblurb
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YW, good luck, and hope it works.
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