2008 S6 AC not working

A6 All/ S6 All
#1

Hey guys!

I’ve got an 08 S6 with AC issues. Noticed it stopped working mid summer last year. I don’t feel or hear the compressor kick on. At a friends shop he added some refrigerant and still not working. We didn’t have time then to dig more.

Common problems that could be causing this if there is no leak?

Anyone that’s been through similar trouble shooting / diagnosis I’d really appreciate the help.

#2

I’ve got an 08 with no AC as well. Currently I’m fighting the 2 codes below of which I have a new AC pressure sensor to go in here soon. I’ll address the flap after that as I’m pretty sure it’s much more involved. I’ve not 100% confirmed it but I’m pretty sure the compressor is kicking on in my case. If you don’t feel like yours is kicking on that certainly could be related. Outside of that you may want to get the car scanned and see if there is anything else that could be contributing.

2 Faults Found:
01274 - Air Flow Flap Positioning Motor (V71) 
        003 - Mechanical Failure
         Freeze Frame:
                Fault Status: 01100011
                Fault Priority: 3
                Fault Frequency: 246
                Reset counter: 135
                Mileage: 256023 km
                Time Indication: 0
                Date: 2021.03.31
                Time: 19:26:55

         Freeze Frame:
                Voltage: 11.20 V
                Temperature: 18.0°C
                (no units): 36.0
                (no units): 162.0
                Temperature: 15.0°C

00256 - A/C Pressure/Temperature Sensor (G395) 
        002 - Lower Limit Exceeded - Intermittent
         Freeze Frame:
                Fault Status: 00100010
                Fault Priority: 3
                Fault Frequency: 3
                Reset counter: 141
                Mileage: 256098 km
                Time Indication: 0
                Date: 2021.04.03
                Time: 20:41:40
#3

A few years ago I lost my ac. Turns out there’s a little plastic tab that can run against the condenser to the point where it will run through and leak out all the cold juice. Diagnosis was easy, anytime I added more freon it would leak out instantly, but would also show where it was leaking from. A new condenser and a razor blade to remove that tab got us up and going again.

#4

Hard to tell when the compressor cycles as it is always running from the shaft coming from the back of the engine (accessory case). Key is to check for faults (Vagcom, etc…), and to monitor the pressure in the system and see if it goes up when the A/C is selected (on the high port of course). There is a plug going to the compressor, I think it’s for pressure reading so check to make sure it is plugged in. As I said, it’s gear driven from the back with a short shaft so it is always turning, no clutch per se. Special procedure when replacing calls for turning it over by had at least 10 revolutions before attaching the shaft, you hold the shaft in place and sping the compressor to thread them together. Don’t try to turn the shaft.