99 Grandprix automatic climate control (Airconditioner) issues, failing AC after periods of time..

We just went through a similar situation with a 98 Buick, although possibly not exactly the same.

The Buick started intermittently failing to put cold air out through the vents, but the blower motor was running strong. Finally intermittent became permanent.

The vacuum module which controls the diverters was not able to overcome the resistance of the mechanical diverters. They were lubricated and freed up, and now the system works pretty much as factory.

IF the freeup job hadnt held, we would have had to replace the vacuum module, and that costs several hundred dollars. This is not an uncommon problem with GM. The POS HVAC computer is another rather common failure.

Interesting tidbit.. thanks...

But in my case, as it works fine on manual.. would this still indicate an Vacuum issue.. I would think it may be more along the lines of the "headunit" or computer itself, which I think I can find a used replacement fairly cheaply?

Cheers

We had the computer replaced a couple of years ago. Ran about $600 new.

Always possibilities at junkyards, if you are careful. If you go to the wrecking yard and find a car with a good (?) vacuum module in it, you might want to pick it up. They are not encased, so do not tolerate rain, exposure, well.

Good luck...Too damn hot here to be without a proper AC.

Thanks...

I did see the climate control computer on ebay used once for around $100, however now I can only find this one:

Roughly $300. This states 1997 GrandPrix, but i think from 97 till

2003? the AC controller unit is the same as in my 99?

How long doe it take for the air to start coming back out again? I have seen several cars where the low pressure switch failed on the a/c. After a while on the hwy the evap would freeze over and you loose air flow. Turn off the compressor for a few minutes and it would thaw out and then you could start the cycle again. Low pressure switch is very cheap and you don't have to drain the system to replace it on most cars (make sure your car is one of those "most" before unscrewing the switch).

Steve B.

Thanks for the tip..

It seems to be about 3-5 minutes for it to come back out full force again, however, I can switch to "manual" mode and have somewhat decent a/c flowing this way, even after it stops coming out, would that still indicate a low pressure switch?