My C5 a/c has always been better than i need, we always joke that it must be the suburban a/c put in a vette. Just drove to Austin, Tx from CC, Tx which is about 3hrs.

after about an hour point five, i realized that the a/c wasnt cold and the fan wasnt blowing jack. it was close to 90 that day and i was stuck to my black leather. really pissed. stopped for a break and a smoke, started her up and it was working perfectly. then about an hour later same thing.

now back from road trip havent had a single problem. Is it possible that the lower engine speed at highway cruise has something to do with it? less current or engine speed.

 

It sounds like your high pressure switch could have been shutting your compressor off. This would explain why it only happens after long periods of running. BUT, there are a multitude of things that could be happening. I think you would have to start by having your freon level checked.

 

I will get that checked, hope that it is that simple. It just seems that if the freon level was low then it would be crappy all the time not just some of the time.

 

and by the way, what is a high pressure switch?

 

AC blows cold at idle. Highway should make no difference. Something is going on, but has nothing to do with driving on the highway. Have the AC checked out.

 

Same thing happened on my BULLITT once... it was the high pressure switch, but not in the way explained above...

The switch shuts the compressor off when pressure gets too high due to temperature of the coolant. It keeps it just above freezing so that your coils dont freeze up. When they freeze the air cannot pass through and get cold. You will still hear the fan blow, but nearly nothing will be comming out the vents as the coils that the air blows through is all full of ice from frozen condensation and air cannot pass through it.

When you stop or park, the ice will melt off. One of the indications that this was my problem on the BULLITT was an EXTREME amount of water under the car after it sat a little while as the ice was melting out of the system.

It never happened around town or on short drives. I would have to be driving constantly for at least 2 hours for enough frozen condensation to accumulate on the coils.

On the BULLITT it was a 5 minute fix, and a $30 part.

 

Sounds like the evaporator is "icing". The condition can be caused by several faults. Start with the easy one first, is the drain below the evaporator plugged? If so, the humidity drawn to the the evaporator cannot drain and becomes frozen thereby blocking air flow over the evap. Your stopping for a smoke for awhile then the S/C worked fine is a tip off. After veryifying drain is clear, look for an overchage state. If too much refigerant in the system the evaporator will become "flooded" and potentially cause the problem too. Good luck, I hope it's the easy fix.

 

I am going to check the drain plug, then will check the coolant for overcharge. will report back. Its going to be sitting for about 2 weeks beforehand cause im off to SERE school in Maine. what a blast.