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A/C turns off when accelerating uphill

Old 07-07-2009, 04:14 PM
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Join Date: Oct 2008
Location: United States
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Angry A/C turns off when accelerating uphill

The A/C turns off when I accelerate uphills. The A/C is also blowing out warm air. Do i need a new compressor? The vehicle is a Automatic, 6cyl, all-wheel drive, 2002 mountaineer.

The compressor cycles ON/OFF OK. The A/C completely shuts off (including the fan) when driving uphill or when it downshifts.
The driver side vents blow cool (not cold) air and the passenger side vents blows out warm air.

Last edited by gl2001_cougar; 07-09-2009 at 02:35 PM.
Old 07-07-2009, 04:58 PM
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Join Date: Oct 2008
Location: United States
Posts: 1,361

you probably have a vacuum leak somewhere or a broken check valve. Unfortunately, there's a lot of stuff to check for this one. the main one is the PCV valve. if it's never been changed, that's going to be a major contributor to your problem. replace it. if it's been replaced recently, don't worry about that one. check all the vacuum lines you can find for cracks/breaks, disconnection. replace the ones that are broken. check valves should allow airflow one way, but not the other. If they allow air to flow both ways, replace 'em. The warm air is probably due to the heater bypass valve on the heater hose not being pulled shut due to the low vacuum pressure and allowing hot coolant into the heater core which will warm the air. This can also be caused by the transmission not downshifting when it should and lugging the engine. This can also be caused by the engine not running well and lugging when it should have plenty of power to spare. weak spark and low compression can contribute to this. Usually it's the vacuum lines though.
Old 07-07-2009, 05:00 PM
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Join Date: Apr 2005
Location: United States
Posts: 859

First you should get a recharge and make sure there are no leaks. How did it work last summer? The compressor you can see by opening the hood w/the a/c on and see if it cycles on and off. I need more detail about it shutting off. Does it stop blowing completely? Always warm? Gave to be accelerating?
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