VW Arteon AC Failure Points to Compressor Issues

Had a very similar issue with my 2019 VW Passat last summer, and being somewhat experienced with AC troubles, I can share what worked for me. The symptoms you describe match exactly what I encountered, complete A/C system failure with compressor not engaging. In my case, the workshop found an undervoltage condition that was causing the AC relay to prevent compressor engagement as a protective measure. The HVAC system has safety protocols that shut down the compressor if voltage drops below certain thresholds. The fix involved: Testing the charging system, Replacing a faulty voltage regulator, Checking the AC relay, Full system diagnostic reset Total repair came to 240€ and solved the issue completely. No problems since then. Before jumping to conclusions about your Arteon though, could you share: What error code exactly showed up? Does the blower motor still work, just no cold air? Have you noticed any other electrical issues like dim lights? When exactly did the problem start? The good news is that in these cases, its often an electrical system issue rather than a mechanical compressor failure. But those details would help narrow things down and confirm if your situation matches what I experienced.

Last service done at 87000km. Thanks for the detailed response and sharing your experience. The scan showed error code P0645. The blower motor works fine, just no cold air at all. No other electrical issues noticed. Problem started suddenly during highway driving last week. The voltage angle is interesting, I had not considered that the A/C compressor could shut off due to an electrical issue rather than mechanical failure. That would explain why there is zero compressor engagement. Will get the pressure switch and AC relay checked first before assuming worst case with the compressor itself. Much rather deal with an electrical fix than full A/C system replacement.

Thanks for providing those additional details about your Arteon. Error code P0645 specifically relates to the A/C compressor clutch circuit, which aligns perfectly with what I encountered in my Passat. The fact that it happened suddenly during highway driving, with no other electrical symptoms, makes me even more confident this matches my situation. The pressure switch and relay testing is exactly the right starting point, these components can fail without warning and cause the A/C system to shut down completely. In my case, though we initially suspected the relay, it turned out the voltage regulator was causing the A/C compressor to disengage sporadically. The repair costs were reasonable because we identified the root cause quickly rather than replacing parts unnecessarily. One quick check you can do: listen near the engine while someone turns the AC on/off. If you hear no click at all from the compressor clutch, this further confirms an electrical rather than mechanical issue. The refrigerant leak check came back normal in my case, worth checking in yours too, as low refrigerant can trigger similar symptoms through the low-pressure safety switch. Let us know what the diagnostic reveals. Based on my experience, you are likely looking at a straightforward electrical fix rather than major A/C system repairs.

I appreciate all the insights, especially about checking for the compressor clutch click sound. Just had it checked at the shop and you were spot on, it was indeed the AC relay that failed. They also tested the charging system and found everything else normal, including refrigerant levels. The repair was pretty straightforward and cost 180€ including diagnostic time. The belt tensioner was also slightly worn so they adjusted that while they were in there, but it wasnt related to the AC issue. Really glad I didnt jump to conclusions about needing a new compressor. The HVAC system is now working perfectly again, cold air blowing strong. Thanks for helping me avoid potentially unnecessary repairs by sharing your similar experience. This forum continues to be an amazing resource for getting to the root cause of issues quickly.