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Old 08-28-2009, 08:47 AM   #1
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AC Runs cold for 20 minutes and then stops

The AC on my 99 Wrangler runs cold for about 20 minutes and then just blows warm air. If I keep driving, about 10-20 minutes later it starts blowing cold again - any ideas?

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Old 08-28-2009, 09:34 AM   #2
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Don't know if this is true or not, but I've been told....

Some models of condenser "ice up" in certain weather conditions (humid, whatever), and when they are in this "iced" condition they can not cool (cool the air/operate properly). When the ice condition melts, they continue to work normally.

I have this problem also. Have never taken it in to be checked since the top is off most of the hot season(s) anyway.

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Old 08-28-2009, 11:40 AM   #3
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i have simillar problem, on mine, its the clutch that get "stuck"...
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Old 08-28-2009, 11:43 AM   #4
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when a/c on, lost off power

i think somebody posted this before but i cant find it. when i have the ac on, the jeep loose a lot of power, very slow at take off and in each gear... any ideas?
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Old 08-28-2009, 12:15 PM   #5
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Make sure your radiator is clear of mud and the like. There are two of them behind the grill one for the a/c and the other for engine coolant. Have your refrigerant removed and flushed. Might be getting some blockage.
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Old 08-28-2009, 12:17 PM   #6
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Quote:
Originally Posted by Loic View Post
i think somebody posted this before but i cant find it. when i have the ac on, the jeep loose a lot of power, very slow at take off and in each gear... any ideas?
I think this is the post you are thinking of.
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Old 08-28-2009, 12:36 PM   #7
Knows a couple things...

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While the a/c compressor can freeze up in humid conditions, it is often more just that it has a small/slow leak and is thus low on R134a refrigerant. If it's low on R134a, it will turn off and on more and if it's low enough, it will stop turning on at all.
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Old 08-28-2009, 01:27 PM   #8
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Quote:
Originally Posted by Zybeon View Post
I think this is the post you are thinking of.
nope not this one ! lol
when the ac is on , the engine is lacking power. at iddle its fine, but then it's like taking off with emergency brake on (maybe not that dramatic but close)
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Old 08-28-2009, 07:26 PM   #9
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I am going to try to make this simple....yeah right..........
There are a few things to look at...
A ref. system is designed with safety switches to protect the system from failure. The switch mentioned above is called a loss of charge switch and will kill the compressor when the pressure gets to low.

Also the compressor has a overload switch that will also kill the comp. when it gets hot. The reason it gets hot is that it requires the cool ref. to do so. If it is low on the ref. of choice it will over heat.

There may also be a high pressure cut out switch that will cut the power off to the comp. if the condenser is dirty the head press. will rise..

If you guys are still with me... let's get into this thing...I hope I have been simple enough

The first thing I would do is get a dummy gauge (the one you would find that comes with a can of R 134a, if the system is or has been retro from 92'. If it is older than 92' and not been retro, you will need gauges for R12)

Install the gauge on the suction port ( larger line off the comp.) Have some one raise the RPM's to 2000 RPMs Then check the reading, the gauge will tell the first symptoms. (I do not have this gauge, but it should go to the green while the comp. is running. (12 O'clockish) It should drop below that for a few seconds than rise a few degrees.

Now we can start...

If it stays below the green mark you are low on ref.. The gauge will slowly drop from there as the capacity of the evap. coil is not being used and the system will slowly ice up. Causing the system to start icing up and the pressure to drop, the loss of charge switch to open. Also the compressor might get hot and the over load might kill it.

If your condenser is dirty or being low on ref., or the cond. fan has stopped running, could cause the high pressure switch to open.

I have tried to explain this before but cannot figure out how to put this into simple form for you guys to understand. I have left you with some of the symptoms and safety's that will cut things off. PM me if you want some more help. Some of this stuff kills me to explain on line. Refrigeration is not easy to comprehend and is hard to sum up in few words.
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Old 08-31-2009, 08:05 AM   #10
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PT4WDL,

You did a good job, thanks.
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Old 08-31-2009, 08:07 AM   #11
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Quote:
Originally Posted by Loic View Post
nope not this one ! lol
when the ac is on , the engine is lacking power. at iddle its fine, but then it's like taking off with emergency brake on (maybe not that dramatic but close)
Do you have a 4 cyl. ?

I do, and this is normal. The A/c drains pedal power.

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