lumpydo

The a/C unit won't click on when I turn it on. I have checked the freon level and the pressure is good. Any suggestions before I resign myself to replacing the compressor?

Redd

One suggestion: Look before you leap.

I learned car AC systems the hard way and that includes getting EPA licensed to work on them.

A modern AC system is chock full of sensors and even it's own computer and there are probably a dozen points that can be the problem, not just the compressor. To replace the compressor you also will need to evacuate the system, pull a hard vacuum in the system, replace the receiver/drier unit, and refill the system and you're talking about significant time and money to do al that--when it may be a total waste since there's no reason to think the compressor is the problem.

The compressor clutch may have failed. The gas pressure switch may have failed. (To Audi's credit that can be removed and tested or replaced without opening the system.) The compressor RPM sensor may have failed. The thermostat may have failed. And the climate control computer may have failed. Or, simply be throwing a fit. And a loose wire to any of that stuff would kill the system too. Or, a bad fuse. And I wouldn't even guess how the computer controls are fused.

I'm all in favor of DIY but when it comes to "modern" auto AC systems? It usually is far cheaper to find a competent shop (I didn't say easy) and let them do the job. And warranty it.

If this is all old news to you, "Nevermind". But really, opening the system and replacing major parts is almost guaranteed to be a huge waste, from what you've said.

lumpydo

Great advice thank you

Prospeeder

These dont have a clutch. They run all the time and have a regulator valve inside. Is the ECON light stuck on? You might check for faults. There is a valve inside the compressor that can fail, and then no a/c. There is also a orifice tube in the system and its in the high pressure line at the firewall, it can clog up. You need to hook up gauges and interpret the pressure readings to determine the issue. A Professional would be best for these types of things.

Redd

"These dont have a clutch. They run all the time and have a regulator valve inside."
Interesting approach. So they have a bypass valve, which directs the refrigerant past the compressor, effectively replacing a compressor clutch? But leaving the compressor running at full speed all the time?

Prospeeder

Yes I believe so. I have noticed a high failure rate of these type of compressors. And alot of them will just lock solid and kick the belt, or some have a built in feature where the center will break away little metal fingers and the pulley will spin freely.

damian-pl

I had the Same Issue and I just fixed it yesterday.. Replaced the High Pressure / Temperature Switch (Audi Dealer Part Number 4H0 959 126 B) which is located in the front grill (drivers side infront of fan).. took me 5 min to replace and the part cost 93$ from Audi.

Can't Believe how long I've been without A/C and it all came down to a faulty little switch, and apparently its a very common problem with these cars.

Redd

How did you diagnose it down to the switch?

Angelbabytk1!

Frustrated here too.. ac not working still.
3rd time in 2 months my 2012 Audi A4 is n the service department at Cavender Audi in San Antonio. Blows cold for 10 minutes then blows warm. They cant figure it out. Recharged freon, sensor,
Any suggestions that will help the service department?!!!😡😡

Redd

"Recharged freon,"
Not enough information, Angel. If they recharged it, that means the system was low, which means there was a leak. If they didn't fix the leak you'd be low again, but that doesn't explain the system failing after ten minutes. And if there was a leak, the receiver/drier would have needed replacing and the system purged as well.
I'd been told that in Texas, car dealers actually hired good AC techs, because the natives would lynch the bad ones, and then go after the management. Especially if this was still under warranty.
Ask AoA if another dealer in your area has a really good AC tech. If they say no...ask them if they really want you to trade the car in on a Chevy.