My AC comes on and then it doesn't

Same issue. In our case, the modulating valve which controls the compressor was going bad. The Tech said it's pretty common. About a $500 repair at the dealer. Works great now.

My 2014 Passat would blow cold for 30-60 minutes in the summer then cut out. In the winter the heater stopped working after 30-60 minutes. If this happens to you, check your AC line. My AC line was freezing up. Easy to tell because the AC line crystalizes and freezes. When the line is frozen, cold and hot air is no longer flowing. If this is your issue, try to get the shop to change out the AC compressor control solenoid, rather than the whole AC compressor. Hopefully this will fix your problem. Most of VW compressors run all the time. The compressor is always engage. No one seems to mention this on any forum. The control solenoid controls how the temperature is regulated in your cars cabin. I spent $1100 to have my compressor replaced (just the compressor). It should have been a $200-300 job to replace the control solenoid, but the shop doesn't make enough money on this job. GuruTHS paid $500, so he/she overpaid too. Good Luck

Im going thru this with my 2015 vw passat LE. My compressor started building up too much pressure. It caused the blow off valve on the ac compressor to blow. It'd start getting this louder noise until it would just start hissing out. I spoke to some online VW tech, he told me it might be the High pressure switch on the line. i replaced that a couple days later same thing. The low pressure was reading high, but it worked great for the day or so until it built up pressure again. I actually put a new compressor on and it got cold. But then, it started getting where it'd only blow cold whenever you would drive down the road. If you ever were at a stop light, it'd just blow warm air. i started to research and finally took it to the VW dealer. I had them to check the fans as sometimes that's an issue when that prob happens. they checked everything and said that it's getting power to the compressor its just that the compressor doesnt seem to be work. i think this thing was bad out of the box or the ac control valve is stuck on it. i was told by another vw tech that the expansion valve might be bad, my brothers shop had had the same issue on a vehicle, they changed the expansion valve and then the AC worked great. So, we changed the expansion valve on mine, and sure enough the expansion valve was stuck. it was bad. So, i'm thinking alright. let's get this thing working. Nope. the damn AC compressor has to be bad at this point. the brand new one i just bought! So, i got to thinking, my old compressor may actually still be good the only reason it was building up pressure and blowing off was because the expansion valve was stuck. So, i ordered a new pressure control valve and i'm just going to replace that on the old one while i have it off as it's much easier to do on the bench. Then, i'm going to empty the compressor , refill it. The old oil in it looks clean as a new one. ill refill it to proper specs and put it back on and see if that fixes the issue. If it does, ill return the ''new'' on for a refund and get my $400 back. we'll see if it fixes it. ill repost if it does.