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Unread 06-24-2013, 07:54 AM   #1
TontoKowalski
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AC only blowing through defrost vents

I hear that it may be a suspect vacuum hose that would make my AC system only blow through the defrost vents...

And, I've read other write up's but still don't really understand where to find or how to look for a faulty area.

I've never dealt with a vacuum system and don't really know how they work. I'm assuming that this system uses air to make a flap open or close that directs the air to the various parts of the vehicle.

What would make a hose within this system rupture? Age?

How on earth do you pinpoint the location where the rupture happened? Soap and water?

Also, any idea what this should cost if I get it repaired professionally?

Thanks ZJs,
JT

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Unread 07-11-2013, 08:12 PM   #2
jamison
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Unread 07-11-2013, 08:59 PM   #3
ZeeJay1997
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it's not air, it is the opposite of air... suckage so to speak.

it starts at the intake manifold. there are some rubber tubes hooked to it . find the one that goes up to the firewall. follow it over to the tee, then into the firewall at the AC lines. if it;s not broken there, follow it further. look for cracks or breakage. it goes under the battery box. it could be broken there too.

does your cruise control work?
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Unread 07-11-2013, 09:11 PM   #4
jamison
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Not to speak for JT, but my cruise works. Although i usually have to press the button around 10 times to get to initially turn on. But it does set and function after that. Thanks for the response.
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Unread 07-11-2013, 09:33 PM   #5
papitt
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I too was thinking that they brake under the battery box . r at the firewall.
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Unread 07-11-2013, 11:00 PM   #6
dellis
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Quote:
Originally Posted by ZeeJay1997 View Post
it's not air, it is the opposite of air... suckage so to speak.

it starts at the intake manifold. there are some rubber tubes hooked to it . find the one that goes up to the firewall. follow it over to the tee, then into the firewall at the AC lines. if it;s not broken there, follow it further. look for cracks or breakage. it goes under the battery box. it could be broken there too.

does your cruise control work?
Adding to ZeeJay's wisdom, this particular hose that goes to your HVAC becomes brittle and often cracks (it looks like the image below, although this is from a Cherokee rather than a Grand Cherokee). It is a 1mm ID x 3mm OD hose, if I recall, about the size of a fuel line for garden equipment. If that is your break, you can replace it or (alternatively), put some shrink tube over it and create a new exterior sleeve.

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Unread 07-12-2013, 08:11 AM   #7
Steve625
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Great pic.. exact location where my line cracked. I did a quick repair in the parking lot of an autozone while I was on a road trip. They did not have the same size hose so I used a hose with the inside diameter that was the same as the outside diameter of the oem line. Find the crack then cut there and use the new the hose as a splint. Been working for over a year so I am leaving it alone.
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Unread 07-12-2013, 05:45 PM   #8
dusterdude
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I always cover that crappy hose with rubber
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Unread 07-12-2013, 06:38 PM   #9
jamison
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That was an awesome pic. I was able to find it pretty quick. Now. When I popped the hose off at the intake I was able to feel quite a bit of pressure sucking. Then after the t split in the picture I kept tracing it. At the cruise I still had pressure. Is there a way to measure the pressure at each of those points and determine the difference to see if there is a leak. At the point below the t it does feel a little rough but I can't tell if it is ruptured at all. And the line appears to dead end under the battery. With a little button that pops up and I assume is pressed down when the battery is in place. Any guesses where go next ?
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Unread 07-12-2013, 06:48 PM   #10
ZeeJay1997
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the bottom of the battery box is a vacuum canister. it is to keep prevent spikes in the lines when the engine has sudden changes in vacuum. The button you speak of is a battery temp sensor.

the line going from the tee that follows the ac lines is your most likely suspect.

there is no pressure to measure. if you had a mityvac, you would be golden.
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Unread 07-12-2013, 06:50 PM   #11
dellis
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Is there a way to measure the pressure at each of those points and determine the difference to see if there is a leak.
Mityvac. It's the best little tool this side of a multimeter.

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Unread 07-12-2013, 06:57 PM   #12
jamison
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ZeeJay, you sir are on your game. Would you recommend I wrap that hose on the engine side of the firewall first. And second I'm assuming the next step would be to disassemble the dash to check the hose on the cabin side of the firewall.
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Unread 07-12-2013, 07:07 PM   #13
ZeeJay1997
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Originally Posted by jamison View Post
Would you recommend I wrap that hose on the engine side of the firewall first. And second I'm assuming the next step would be to disassemble the dash to check the hose on the cabin side of the firewall.
if you can see a break near the hole in the firewall,, you can fish it out enough to slip a piece of suitably sized hose over it and make a splice. IIRC, you can access the area you need to get to by taking the radio out. Not sure.
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Unread 07-12-2013, 09:04 PM   #14
Uniblurb
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Quote:
Originally Posted by ZeeJay1997 View Post
if you can see a break near the hole in the firewall,, you can fish it out enough to slip a piece of suitably sized hose over it and make a splice. IIRC, you can access the area you need to get to by taking the radio out. Not sure.
That's what I did Zee and was lucky enough to fish the small black plastic tube back up with small needle-nose. I don't think you can access that area by removing the radio since the bolts on the box going through the firewall have the box pulled up so tight against it.

The black plastic line goes right over-top the HVAC box from the AC evaporator tube hole and is attached under a plastic hook/clip on the box up under the glove box. If you've lost the line completely I found it best to use a piece of small stiff wire and fish it through the outside firewall hole. Then tape a new piece of line to it and pull it through. Can't use regular vacuum line because it's too big to pull through but can use it for the splice while taping it real good with electrical tape.
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Unread 07-13-2013, 10:56 AM   #15
Billyjoebob007
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You need to install a check valve.

http://dodgeram.info/tsb/1996/24-01-96a.htm
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