RS4 AC System Dead, Owner Seeks Troubleshooting Help

Had a similar issue on my 2019 Audi S4. The blower motor stopped working completely, leading to no airflow and temperature control failure. After inspection, the problem turned out to be a faulty pressure switch in the AC system. This prevented the compressor from engaging, resulting in complete cooling system shutdown. The pressure switch acts as a safety mechanism, and when it fails, it keeps the entire AC system from operating. Initial symptoms included: No cold air output, System not engaging at all, No compressor clutch activation sounds The repair required: Pressure switch replacement, System evacuation, Recharge with fresh refrigerant, Full system diagnostic This was a serious repair since the faulty switch could have allowed the compressor to run without proper pressure protection, potentially causing major system damage. The cooling system needed complete servicing to ensure no contamination remained. Before heading to a mechanic, check if the fuses are intact and listen for any AC noise when turning the system on. However, given the complete system shutdown, its likely a component failure requiring professional diagnosis and repair.

Thanks for sharing your S4 experience. I recently had my RS4 repaired for what sounds like the exact same issue. The AC relay was actually the culprit in my case, requiring replacement along with a full system check. Did you remember what the final cost was for your repair? Also curious if youve had any other AC efficiency issues since getting it fixed? Mine has been running perfectly for the last 10000km, but Id like to know what to watch out for.

After getting my S4 fixed, the AC diagnostics revealed several faulty valves in the cooling system rather than just a pressure switch issue. The complete repair, including labor and parts, came to 1000 Euro. This covered the valve replacements, system evacuation, and a fresh refrigerant charge. The AC has been working flawlessly since the repair, no refrigerant leaks or efficiency problems to report. The shop did a thorough job checking for potential issues during the diagnosis, which helped prevent future problems. The AC relay and all other components were tested and confirmed to be in good condition. The investment was worth it since the system now cools quickly and maintains consistent temperature. No unusual AC noise or performance issues have surfaced in the 30000km since the repair. Regular maintenance checks help ensure everything stays in proper working order.

Thanks for the input. Just wanted to share how my AC repair went at the dealership. Turns out the AC diagnostics showed a failed relay and some minor electrical issues in the cooling system. The whole repair including parts and labor ended up being 450 Euro. The mechanic was really thorough and found the problem quickly. They did a complete system pressure test and showed me exactly where the relay had failed. Unlike my previous repair experiences, they took the time to explain everything. Its been about 2 months and 10000km since the fix. The AC is working perfectly now, no strange AC noise, consistent cooling, and the blower motor runs smoothly at all speeds. Definitely glad I got it sorted before summer. For anyone facing similar issues, I recommend getting a proper diagnosis rather than trying quick fixes. The complete shutdown of my system was actually a blessing in disguise since it prevented any potential damage to the compressor.