Audi S6 Heating Failure Points to Water Valve Issue

I dealt with a very similar heating issue on my 2012 Audi S8, which shares many components with your S6. I have some experience working on these types of problems, though I typically rely on professional help for complex repairs. The symptoms you describe match exactly what I experienced, minimal cabin heating and issues with engine coolant circulation. In my case, the problem turned out to be a faulty electrical connection to the heater control valve. The cable connection had corroded over time, preventing proper valve operation. My workshop diagnosed and fixed the issue for 95 Euro, which included: Testing the electrical connections, Replacing the damaged wiring connector, Verifying proper coolant flow, Final system check Before taking it to the shop, you can check a few things: 1. Listen for the water valve clicking when changing temperature settings 2. Check if the engine coolant level is correct 3. Feel both heater hoses (when cold) to ensure there is no obvious car valve blockage Could you share: Current coolant temperature readings? Whether you notice any coolant leaks? If the heating works better at higher engine RPMs? This information would help determine if you are facing the same electrical issue or potentially a different problem.

Thanks for the detailed reply. My previous service was 2 months ago at 168000 KM. After checking as suggested, I confirmed the cooling system is working inconsistently. The heater core seems warm on one side but cool on the other, suggesting a potential valve blockage. No visible coolant leaks anywhere, but coolant temperature reads slightly higher than normal at idle. Heating does improve a bit at higher RPMs. Going to book a workshop appointment since testing revealed the car valve might need more than just an electrical fix. Will have them check the entire coolant flow system to prevent any major issues down the line.

Thanks for the update. Those symptoms on your S6 definitely point towards more than just an electrical connection issue like I had on my S8. The temperature difference you are experiencing across the heater core is a classic sign of restricted coolant flow, which aligns with my previous suspicion about valve issues. After my initial electrical fix, I actually encountered a similar problem 6 months later. The automotive valve itself had partially failed, creating inconsistent coolant flow patterns. The repair involved: Full cooling system flush, Replacement of the main control valve, New engine coolant, System pressure testing Total cost was around 320 Euro, but it completely resolved the heating performance issues. The improved flow through the heater core made a huge difference in cabin heating efficiency. A word of caution based on my experience: have them check the thermostat while they are working on the cooling system. These components often fail around the same mileage point, and replacing both at once can save labor costs if needed. Let us know what the workshop finds. This information could help others with similar valve blockage issues.

Thanks for the helpful advice. I wanted to close this thread with an update after getting the car checked at the workshop. The issue was indeed more complex than just an electrical problem. They found that the water valve had partially seized, restricting engine coolant flow to the heater core. The repair included: Complete system flush, New water valve installation, Fresh coolant fill, Full pressure test Total repair cost was 295 Euro. The cabin heating now works perfectly, with strong consistent heat output. The coolant temperature also now stays within normal range. For reference to others who might face similar issues: The key warning sign was the uneven temperature across the heater core. Getting this fixed promptly helped avoid any potential damage to other cooling system components. Really appreciate all the input that helped diagnose this problem before the workshop visit.