A/C Odd Problem! 3800 V6

[cruzkit]

Greetings:

I have a 1999 Pontiac Grand Prix 3800 V6 with an odd a/c problem. The car was just tuned up about a year ago and I change the oil about once every 6 months. The cars a/c was working fine when suddenly it stopped working...kinda of...It works sometimes...I went off and got the feon charged (at Jiffy lube) and the worker double checked for leaks..The worker said it should be working fine. No loss of pressure/no leaks. Oddly now the a/c only still works just some of the time...The outside temp reads normal, a/c button is on yet I get nothing but blowing hot air...sometimes...I just went on freeway a few days ago and suddenly the air suddenly turn cold! Cold air from all vents-It was working like normal. The next day nothing but hot air again!
So I quickly went to a mechanic (GM Dealership) with the air running cold and after a few checks he says it's probably the compressor and he will replace it for $1100.00 (!!!) He said he wasn't 100% sure tho!

Any ideas?

Thank You!

[richtazz]

Welcome to AF.

Get a second opinion. If he's not sure what the problem is, why would you pay him $1100 to guess?

The problem with intermittent issues is that it's hard to offer advice without hands-on time. Most A/C problems are beyond the abilities of the DIY because of the specialized equipment needed to properly test.

[tblake]

Manual or Digital Automatic HVAC unit?

[cruzkit]

Thanks for the information! Great to have found this place!

Once again today I reved up my engine and the a/c started working!
It blew nice cool air from all the vents and everything seemed normal once again...until it stopped working tonite...

Very strange.

Digital Automatic is what I have.

I will also get a second opinion from another mechanics...
For a moment I was sure I saw dollar signs in the mechanics eyes!

Thanks again!

[brcidd]

A/C intermittents can sometimes be traced to a compressor clutch air gap that is worn too wide- look at front of compressor- is gap between driver and pulley more tha .050" Two or three business cards slip into it-- if so that is probably what is wrong.

Next time a/c is inop- strike the front of the compressor with a blunt object- (or hit a bump- or slam the hood) - see if air starts working....and report back.

[tblake]

But if the compressor air gap was too wide, wouldnt it hold better at idle and not at higher RPM's?

[brcidd]

its not that it is holding-- it is not closing the gap and engaging....

[CrazyHorst]

If you have a data scanner (not sure which ones have this data...I'm only familiar with Tech 2s up to now) that can read the clutch command (ON/OFF) and the high and low pressure switch values...you can start making some more educated guesses about what's wrong.

Depending on your level of parts changing skill, an AC compressor can be done with new/reman AC Delco for a lot less than $1100. I paid $65 to have my GTP recharged earlier this spring after a compressor replace and ~$30 from a GM dealer for the PAG compressor oil. The parts came from rockauto.

[rkvons]

How do we know it isn't the control unit sending hot air in when it's supposed to be sending cold air in? The digital units seem to have minds of their own sometimes.

[rkvons]

Try disabling the "Automatic" setting. Then crank the temperature down to complete cold and back up to hot and see if the temperature of the air coming out follows you. You can pull the HVAC fuse, wait a minute and then put it back in and give that a try.