VW Touareg A/C Compressor Dead, DIY Diagnosis Help

Had the same issue on my 2012 VW Tiguan last summer. The symptoms matched exactly, no compressor engagement and zero cooling. After diagnostic testing, it turned out the AC relay switch was failing due to undervoltage in the HVAC system. The relay switch serves as the power connection between your climate controls and the air conditioning compressor. When it fails, the compressor wont engage even if the rest of the system is fine. Before replacing the entire AC compressor, have a shop check: 1. AC relay switch functionality 2. System voltage at the relay 3. Low pressure cutoff switch 4. Refrigerant pressure levels In my case, replacing the relay switch and recharging the A/C system solved the problem completely. This was much simpler than a full compressor replacement. The repair wasnt particularly complex, but proper diagnosis was crucial to avoid unnecessary parts replacement. Your symptoms strongly suggest a relay or electrical issue rather than mechanical compressor failure, especially given the vehicle age and mileage. Getting these electrical components tested first could save significant repair costs.

Thanks for sharing your experience. The symptoms do sound identical to what I had with my 2009 Touareg. Quick question, do you remember roughly how much you paid for the AC relay replacement and recharge? Also curious if your A/C system has been running smoothly since the repair or if you noticed any other issues? My belt tensioner is also making some noise, so trying to figure out if I should have that checked while the mechanic looks at the air conditioning.

Good news regarding the A/C compressor issue on my Tiguan, after getting the undervoltage problem fixed at the shop, the HVAC system has been working flawlessly. The total repair cost came to 240€, which covered both the diagnostic work and fixing the relay switch issue. The air conditioning runs perfectly now, the compressor engages immediately when needed and maintains consistent cooling. No other problems have surfaced since the repair was completed. Regarding your belt tensioner noise, absolutely get that checked while they inspect the A/C system. A failing tensioner can actually cause additional stress on multiple components, including the air conditioning compressor. The pressure switch and other parts of the cooling system rely on proper belt tension to function correctly. The relay switch repair ended up being much more cost-effective than replacing the full A/C compressor, which would have been unnecessary in this case. Having a proper diagnosis made all the difference in keeping the repair costs reasonable.

Finally got my Touareg back from the shop. The mechanic confirmed it was indeed the relay switch causing the A/C compressor issues. Total bill came to 280€ including diagnostic work, replacing the relay switch, and recharging the A/C system. They also checked the belt tensioner while the car was in, good thing too since it was starting to wear. Had them replace that as well since they were already working in that area. The A/C system is now working perfectly, strong cooling and the compressor engages right away. Much better experience than my last mechanic who wanted to replace the entire A/C compressor without proper diagnosis. Really glad I asked here first and got that helpful advice about checking the relay switch and pressure switch before jumping to bigger repairs. The proper diagnostic approach definitely saved me from an unnecessary expensive repair.