VW Phaeton AC Dead: Relay vs Major System Failure

I had a similar issue with my VW Passat 2009 last summer. The AC system completely stopped functioning, showing symptoms identical to yours. After inspection, it turned out to be more than just a relay problem, the expansion valve had failed, leading to a complete cooling system shutdown. The diagnosis revealed multiple issues: The expansion valve was stuck closed, This caused excessive pressure in the AC system, A refrigerant leak developed at one of the seals, The system automatically shut down to prevent compressor damage The repair required: Replacing the expansion valve, Fixing the refrigerant leak, Recharging the AC system, Testing AC efficiency after repair This was definitely a serious issue that required immediate attention to prevent further damage to the AC components. When getting yours checked, make sure they: Test the relay first, Check refrigerant pressure levels, Inspect all valves and seals, Verify compressor operation For proper AC maintenance going forward, regular system checks are essential. The low mileage on your Phaeton suggests this could be age-related deterioration rather than wear and tear.

Thanks for sharing your experience. The problem with my AC was very similar, our symptoms match exactly. The blower motor and pressure switch ended up needing replacement, plus they found a leak that had to be fixed. Did you notice any other issues since the repair was done? Also, could you share what the total repair cost was? Just want to get an idea of what to expect when I take it in.

The complete AC diagnostics revealed problems with individual valves which matches the symptoms we both experienced. After paying 1000€ for the repair three months ago, the temperature control system has worked flawlessly. The pressure switch replacement and valve repairs completely resolved the cooling system issues. Regular AC maintenance checks since then have shown everything working properly. No refrigerant leaks or pressure problems have occurred after the fix. The repair cost was significant but necessary to prevent more expensive compressor damage. Getting the valves fixed early likely saved money in the long run. The mechanic thoroughly tested the entire system after the repairs, which helped identify and correct all issues during a single service visit. The AC now maintains consistent cooling performance even during extended use.

I took my Phaeton to a certified shop last week and the diagnosis matched what you described. The total repair cost came to 1200€, higher than expected but they did a thorough job. They found a cracked pressure switch and fixed a significant refrigerant leak in the system. The AC efficiency is much better now. The temperature control works perfectly and the cooling is consistent. The shop did complete AC diagnostics including pressure testing and electronic system checks. They also showed me the worn parts they replaced, which helped justify the cost. Getting that second opinion before the repair really paid off. The cooling system is working like new and I actually saved money by catching these issues before they could damage the compressor. Will definitely keep up with regular maintenance checks from now on.