Brought my 02 Allroad in for an AC repair and the tech told me that since the battery light came on every now and then that the charging system could drop low enough to turn off the compressor. The AC shuts off when it is very hot outside. Suspected the high pressure switch to be faulty and failing or falsely reading when it is hot. System has been completely evacuated and charged by the professionals and it still cuts out. Could the alternator be going bad and shutting down the AC even when the battery light doesn't come on. The tech said that the light only comes on at a certain voltage but before the light comes on, the computer can still cut out the compressor.

I asked if they tested the high pressure switch and he said the pressures are fine. I think that the pressures can be fine, hence the switch actually failing.

What do you think?

 

Well...I just had the shop install the high pressure switch. We shall see if that solved the issue.

 

It could be that the alternator is on its last legs. It makes sense that the ecu would kick the compressor off since it puts a high load on the engine. Obviously the alternator charges the electrical system and the less stress the engine has the easier and faster it can spin the alternator.

Has the vehicle been scanned with VAG-COM? I'd imagine there would be some codes that might help pin point the underlying issue.

Jason