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Old 04-01-2013, 10:34 PM   #1
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Air switches to defrost when engine under load

So I've been noticing that when I have the air on it'll change to defrost when the engine is user load, like accelerating hard or going up a hill. I'm assuming it's some sort of vacuum thing because from what I've read the air modes are vacuum related. Any ideas on where to start looking?

The air also takes a long time to switch between output locations, like from defrost to face or from feet to face.

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Old 04-02-2013, 04:22 AM   #2
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i'm a mechanic and have seen this before. there is alittle valve in the vacum hose going into the dash that goes bad. you will probably have to buy the harness from jeep.

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Old 04-02-2013, 04:57 AM   #3
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Do a search on vacuum. There are diagrams of the vacuum system and where to look in posts.
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Old 04-02-2013, 05:35 AM   #4
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Any idea what that valve may be called so I can look it up?
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Old 04-02-2013, 06:08 AM   #5
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Vacuum Check Valve best to get from Dealer (Not a expensive part)
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Old 04-02-2013, 07:50 AM   #6
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Quote:
Originally Posted by eugenesonrisa View Post
Any idea what that valve may be called so I can look it up?
I wuld check just the vacuum lines first. I had the exact same problem when I bought my Jeep last year and for about $2 I bought vacuum line and replaced the piece that was bad.
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Old 04-02-2013, 07:51 AM   #7
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You've got a vacuum leak. Most likely at the vacuum reserve canister.

Lay under your jeep behind the front pass tire. Look up along the frame for a single hose sticking out. If it is cracked either replace the hose or wrap it tight in tape.

Read this thread I posted a diagram in it. The connection I'm referring to is the box labeled 8. http://www.wranglerforum.com/f5/ac-question-228922.html

If there's no crack there follow the line until you find it.
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Old 04-03-2013, 11:54 AM   #8
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Thanks everyone for the help.
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Old 04-03-2013, 11:54 AM   #9
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I'll check into all this. Thanks for the help.


Dang interweb playing tricks on me.
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Old 04-03-2013, 01:41 PM   #10
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Quote:
Originally Posted by Hardermods View Post
You've got a vacuum leak. Most likely at the vacuum reserve canister.

Lay under your jeep behind the front pass tire. Look up along the frame for a single hose sticking out. If it is cracked either replace the hose or wrap it tight in tape.

Read this thread I posted a diagram in it. The connection I'm referring to is the box labeled 8. http://www.wranglerforum.com/f5/ac-question-228922.html

If there's no crack there follow the line until you find it.
x2, it's either the vacuum reservoir and/or check valve. The reservoir is located in the passenger fender, it's easiest to get to by removing the battery.

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