Audi Q8 AC System Total Failure, DIY Diagnosis Help

Had a similar AC system failure in my 2015 Audi Q7 3.0 TFSI. The complete AC shutdown pointed to multiple issues during AC diagnostics. The main problem was defective expansion valves, which prevented proper refrigerant flow through the system. Temperature control was completely lost because the valves were stuck closed. After thorough testing, we found that corrosion had damaged the valve assembly, affecting both refrigerant flow and pressure regulation. This is actually a known issue in these models. The repair required replacing the expansion valves and performing a full AC maintenance service. The technician also discovered a small refrigerant leak at one of the connection points. This was indeed a serious issue that required specialized tools and expertise to fix properly. For your Q8, start with checking the AC relay and fuses since the system wont engage at all. If those check out, you likely need professional AC diagnostics to test the expansion valves and pressure switches. The symptoms match what I experienced, complete system shutdown is often linked to either electrical problems or major valve issues. A professional inspection will quickly determine if its a simple relay problem or more serious internal damage. Given these models share similar AC components, Id strongly recommend getting it properly diagnosed rather than attempting temporary fixes.

Thanks for sharing your Q7 experience. The expansion valve and refrigerant leak issue sounds exactly like what my blower motor started doing. The temperature control and AC efficiency were completely off until I got it fixed. The AC noise was also getting worse before the total failure. My Audi Q8 needed similar repairs to yours, new expansion valves and a full cooling system service. Would you mind sharing what the repairs cost you? Just wondering if prices have changed much since then. Also curious if youve had any other AC problems since getting it fixed? Mine has been running great for a few months now but always good to know what to watch out for.

Finally got around to sharing the repair costs for my Q7s AC system. The total came to around 1000 Euro for replacing the defective valves in the air conditioning system, which matches what others paid for similar repairs. The good news is the cooling system has worked flawlessly since the fix. The temperature control is perfect now and the AC diagnostics showed no other underlying issues. The blower motor runs quietly and the AC relay is functioning as it should. Its been over 2 years since the repair and I havent experienced any other AC problems. The key was getting a proper diagnosis and complete fix rather than just temporary solutions. Regular maintenance has kept everything running smoothly since then. Great to hear your Q8 is also running well after similar repairs. These Audi AC systems are quite reliable once properly fixed, especially when all components like the expansion valves are properly maintained.

Thanks everyone for the helpful replies. Just wanted to share how my repair experience went after all your advice. Took it to a repair shop that specializes in German cars. They ran a full AC diagnostics check and found the expansion valve was indeed shot, plus there was a significant refrigerant leak in the cooling system. The blower motor needed cleaning but wasnt actually damaged. Total repair bill came to 1200 Euro which included replacing the AC relay, fixing the refrigerant leak, and doing a complete system service. More than I wanted to spend but worth it to have everything working properly again. AC has been running perfectly for the past 3 months, no strange AC noise or temperature control issues. The shop also showed me what to watch for in the future to catch problems early. Really glad I got it properly diagnosed instead of trying quick fixes. Thanks again for steering me in the right direction with this!