1995 Pontiac Trans Am Air Condition stops working after run

JOSH95TRANSAM

MEMBER
1995 PONTIAC TRANS AM
V8
2WD
AUTOMATIC
143,000 MILES

I have a 95 pontiac trans am. The AC works for about 10 mins when I start the car up in the mornings. But once the car has warmed up the AC will stop blowing cold. I've checked and it has enough freon. When the AC is blowing cold and I stick the pressure guage on it reads normal. But once the AC stops blowing cold and I put the pressure guage on it the pressure guage reads maed out. What could be causing this? Do I need a new AC compressor?

7 Replies

MATHIASO

MECHANIC
1,209 POSTS

Hello Josh95Transam

An A/C system that blows cold air for awhile then warm air is probably freezing up. This can be caused by air and moisture in the system that allows ice to form and block the orifice tube.
Evacuating the system with a vacuum pump will purge it of unwanted air and moisture. Evacuation should be done with a vacuum pump that is capable of achieving and holding a high vacuum (29 inches) for at least 30 to 45 minutes.
For best performance, an A/C system should contain less than 2% air by weight. For every 1% increase in the amount of air that displaces refrigerant in the system, there will be a corresponding drop of about one degree in cooling performance. More than 6% air can cause a very noticeable drop in cooling performance, and possibly cause evaporator freeze-up.

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Monday, February 22nd, 2010 AT 9:58 AM

JOSH95TRANSAM

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I don't think that's the problem because I can start up the car leave the AC complete off and then turn the AC on 20 mins later and all I get is hot air and the guage reads that I have to much pressure once the AC starts blowing warm air.

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Monday, February 22nd, 2010 AT 11:22 AM

MATHIASO

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I do not understand this" But once the AC stops blowing cold and I put the pressure guage on it the pressure guage reads maed out". What do you mean by

''pressure gauge reads maed out?"

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Monday, February 22nd, 2010 AT 11:01 PM

JOSH95TRANSAM

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Maxed out. Like there's way to much pressure in the line.

But evermind disregard my second post because I let the TA run for 40 mins with the AC off and then turned it on and it blew cold. But then let it run with the AC on and it stopped blowing cold air after about 20 mins. So your right it's freezing up.

It would be the evaporator valve that is freezing up right and isn't that under the passenger side dash?

I just wanted to take a look at it to see if I did see that it was frozen because I remember having my AC unit in my apartment freezing up some times and you could open it up and see everything frozen.

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Tuesday, February 23rd, 2010 AT 8:26 AM

MATHIASO

MECHANIC
1,209 POSTS

Hello Josh95Transam

Too much pressure explains also that the system is freezing up, probably the evaporator and it may be caused by moisture in the system.
Replacing the evaporator will not solve the problem because a special vacuum pump must be used to get moisture out of the system anytime the air conditioning system is opened also the federal clean air act prohibit opening the air conditioning without proper equipments and there is a fine and money to the whistle blower.
What you need to is to take your car to a shop and let them clean clean and evacuate the system and you can take it home and charge it yourself.