Weak RS4 Heater Core Needs Expert Diagnosis

Had the exact same heating issue on my 2009 Audi S4. The engine coolant wasnt properly circulating through the heater core because of a faulty automotive valve connection. The check engine light appeared due to the disrupted coolant flow. Initially thought it was just a heater core blockage, but diagnostic tests revealed the car heating system had multiple problems. The main culprit was a damaged wiring harness connecting to the coolant control valve. This created irregular temperature readings and poor heat distribution. The repair required replacing both the wiring harness and the automotive valve assembly. It was a serious repair that needed specialized diagnostic equipment to properly identify all failing components. The car stayed at the garage for 3 days due to the complexity of accessing and testing the entire heating system. After the fix, the car heating performance returned to normal and the check engine light cleared. Would recommend getting a complete diagnostic test rather than just replacing parts, as these heating issues often involve multiple connected components in the coolant circulation system.

Thanks for sharing your experience. Mine turned out similarly, the coolant leak was spreading beyond just the heater core area. Makes me think there might be a common weak point in these models. Have you noticed any other issues cropping up since the repair? Also, if you dont mind sharing, what did the total fix end up costing? My mechanic gave me a rough estimate but Id like to compare before committing to the work.

After getting the water valve defective fixed last month, the heating system has worked flawlessly. The engine coolant now circulates properly, and the temperature stays consistent. The repair was much simpler than initially feared, just needed a new cable connection to the coolant control valve, which cost 95 Euro including labor. The cooling system hasnt shown any other problems since the fix. No more check engine light, no engine overheating issues, and the heat works perfectly even on cold mornings. The mechanic mentioned these valve connections are a known weak point, but once properly repaired, they typically last for years. Just make sure your technician checks the entire coolant flow system while doing the repair. Sometimes what appears as a simple valve issue can mask other developing problems in the cooling circuit.

Thanks for the input. I took my car to a different mechanic this time who specializes in German vehicles. Turns out the main issue was actually a combination of problems, a failing automotive valve and a small coolant leak near the heater core connection. The total repair came to 380 Euro, which included replacing the valve assembly, fixing the coolant leak, and a full system pressure test. They had the car for about 4 hours and did a great job explaining everything. The engine overheating warning has cleared completely and the heating now works better than it has in years. Much better experience than my last repair shop visit. No more cold morning drives for me. The car heating system finally works the way it should.