Hey guys,

Here's the deal, I had my A/C fixed back in April. They said I needed a new compressor and high pressure switch (the one on the radiator.) When they were done the A/C worked great. Now, for the past 2-3 months I haven't had A/C. When I originally took it back to him he said there wasn't anything wrong with the A/C that it was a "driveablilty" issue. So I have had everything checked out and have traced all vacuum leaks myself and fixed EVERY little vacuum leak. The car is running perfect minus the A/C.

The problem is that the a/c works while it cold out (which does me no good.) When its hot out and I turn the a/c on, it works for about 10 minutes, then as I come to a stop, the idle gets rough until the a/c quits. If its idling rough and I hit 'econ' the idle goes smooth.

Help me out guys, I'm at a loss

Mike

 

Anyone have any thoughts?

 

What climate do you live in? The A/C is designed to turn off automatically if the little snow flake in the cluster is on. This is to keep the evaporator from freezing up. If you are running the A/C somehow and bypassing the safety shut off you could be damaging the compressor and making the engine drag. Look at the belt and the A/C compressor pulley for any damage on the belt, and heat spots on the compressor. If you notice any damage take it to the dealer and get a second opinion, they may have done a hack repair which they could be responsible for.
Other than that i can't tell whats wrong with it without seeing the high and low pressures in the system.

 

Well, I'm in Tampa, FL so freezing is outta the question. I see that little snow flake for a total of about 2 minutes a year. The belt is in perfect shape, but I will check out the compressor for any heat spots. What has me lost is that when I took it back to him he said everything in the a/c system checked out fine. That's why he told me it had to be something other than the a/c. But how can it be when the rough idle only occurs when the a/c is on?

 

In the other car that I have lots of experience with, the mazda rx-7, there is a part called the bypass air control valve that allows extra air into the motor to eliminate bogging down when there are loads on the engine such as the ac coming on. On that car, if this part didn't work properly, anytime the ac came on or there was a heavy electrical load the car would basically run like crap at idle.

Kinda sounds like what's happening to you, but I'm not sure if the a4 has anything like that BAC valve.

 

Shane, would that valve cause the a/c to stop working? because when I'm at idle with the a/c on, after a couple minutes the idle gets really bad, and you can hear what kinda sounds like a low-tone whinning, then the a/c compressor turns itself off.

 

No. My best guess at this point would be a faulty compressor. When the ac "quits" does it just stop blowing cold or does the clutch on the ac pulley actually disengage? Sounds to me like your compressor does not want to turn which is causing the noise, and therefore causing a lack of circulation of refrigerant which would cause the warm air.

I don't have much experience with ac systems though...

 

That's a really good question....I will check that as soon as I can. I was thinking it was the compressor myself, but the guy said the compressor was fine, so I dunno. I'm tempted to take it to the dealer at this point and see what they say.

 

I would take it to the dealer, just because shops perform A/C repair work doesn't mean they are qualified to diagnose A/C systems. It could be overcharged, undercharged, too much oil in the system, not enough oil in the system, or the A/C compressor could be shot. However the ECON button will stay lit when the A/C system either runs out of refrigerant or the A/C compressor stops working.

 

Well, this guy specializes in A/C work, so I know he is qualified to work and diagnose A/C systems. He's done work on other cars of mine and I've never had any problems. I think I'm gonna give him one more shot to figure it out, then I'm gonna take it to the stealership to see what they say.