VW Crafter AC System Failure: Compressor Issues Alert

I had a similar issue with my 2020 VW Transporter last summer. Having moderate experience with HVAC systems, I initially thought it was the A/C compressor too, but it turned out to be an undervoltage problem affecting the entire system. The diagnostic scan showed similar error codes, and the A/C would completely fail to engage. After taking it to a workshop, they found the root cause was electrical, the pressure sensor and pressure switch were getting insufficient voltage, causing the system to stay in safety mode. The fix involved: Testing the electrical system, Replacing a faulty voltage regulator, Recalibrating the pressure sensor, Checking the A/C compressor operation, Recharging the system Total cost was 240€ and the repair took about 3 hours. The A/C has worked flawlessly since then. To better assist with your specific case, could you share: The exact error code from your diagnostic scan, Whether you notice any unusual sounds when trying to engage the A/C, If the belt tensioner appears to be working normally, Whether this issue started suddenly or developed gradually, If you notice any other electrical issues in the vehicle This information would help determine if your problem is similar to what I experienced or if its something different.

Thanks for checking my issue. My mileage is indeed 126233KM and had my last service just 2 months ago. The error code shows P0645 which points to an AC relay circuit malfunction. No unusual sounds when engaging the AC. The belt tensioner seems normal with proper tension and movement. The issue started gradually over the last week, first intermittent operation, then complete failure. The relay switch theory makes sense since there are no mechanical noises or visible issues with the A/C compressor. No other electrical problems noticed in any other systems. Would testing/replacing the AC relay be a good first step before diving into more complex HVAC system diagnostics?

Thanks for those details. I had almost identical symptoms with my VW Transporter before discovering the relay problem, particularly the gradual failure pattern starting with intermittent operation. The P0645 code definitely points to the AC relay circuit, which aligns perfectly with the symptoms. In my case, testing the relay switch showed it had failed, causing similar issues with the HVAC system engagement. Replacing the AC relay was indeed the correct first step and solved the problem completely without needing to explore other components. A failing relay often shows these exact symptoms: No compressor engagement, No unusual mechanical sounds, Normal belt tension, Gradual deterioration of AC operation, No refrigerant leak or pressure issues The repair was straightforward and cost-effective, around 85€ including labor. Testing the relay is definitely the smart first step before investigating more complex issues like compressor failure or electrical system problems. Just ensure to check the relay connections for corrosion while replacing it. In my case, there was slight corrosion on the terminals which could have contributed to the failure.

Your diagnosis and suggested repair path seem spot-on. The P0645 code combined with the perfect operation of all mechanical components strongly suggests an AC relay problem. The gradual failure pattern matches what others have reported with relay issues. I will buy a new relay this week and have it installed. The 85€ cost estimate sounds reasonable compared to what a full A/C compressor replacement would cost. The lack of any refrigerant leak or strange noises makes me confident this is an electrical rather than mechanical issue. Will test the new relay and check those terminal connections carefully during installation. Really hoping this fixes the problem without needing more extensive repairs to the A/C system. Will report back on the results once the repair is complete. Thanks for confirming my suspicions about the relay being the likely culprit.