Audi A7 Cooling System Issues: Multiple Sensor Failures

I dealt with a very similar issue on my Audi A6 3.0 TFSI from 2016. Having some experience with vehicle maintenance, I initially thought it was just a coolant leak, but it turned out to be more complex. The symptoms matched yours exactly, cooling system warnings, AC problems, and error codes. After multiple diagnostic attempts, my workshop found the AC control unit had failed, which was affecting the entire temperature management system including the heat exchanger sensors. The repair process involved: 1. Full system diagnostic scan 2. Removal of front bumper components 3. Replacement of the AC control unit 4. Recalibration of the cooling system 5. Testing all temperature-related functions Total cost was 980 Euro including parts and labor. The repair took about 6 hours to complete. Since then, all systems have worked perfectly. Could you share: Current mileage on your A7? Any unusual sounds from the AC system? When did you last have the coolant changed? Are there any other warning lights active? This information would help determine if your issue is identical to what I experienced and whether you might need the same repair path.

After 198570KM and my latest service just last month, I think you might be onto something with the AC control unit suggestion. The sensor calibration process you described matches what my mechanic initially suspected. The engine cooling system had been working fine until these issues started, with no obvious coolant leak visible. I am not hearing any unusual sounds from the AC, but the temperature sensor readings seem erratic in the diagnostic reports. My warning lights only appear when trying to activate the AC, no other alerts are showing up. Based on your experience, I will have my mechanic check the AC control unit specifically. The repair cost you mentioned seems reasonable considering the complexity of the work involved. Would you recommend checking anything else while the system is being diagnosed?

Thanks for the additional details about your A7. Since we seem to have identical issues, I can share some extra insights from my repair experience. The mileage on your vehicle is very similar to when my AC control unit failed, mine was at 189000KM. The erratic sensor readings you mentioned are a telltale sign of the control unit problem, as it affects the entire HVAC system communication. During my repair, we discovered a few additional components worth checking: The wiring harness connecting to the heat exchanger showed minor corrosion, Several small vacuum lines had become brittle, The sensor calibration required a software update One important note, while the engine cooling system worked normally, the failing control unit was sending incorrect data to the vehicle computer. This triggered the safety protocol, preventing AC operation. The repair cost might vary slightly based on the condition of surrounding components, but expect around 900-1100 Euro. Make sure your workshop performs a complete HVAC system pressure test after the repair. Also, while the front end is apart for access, consider having them inspect the radiator and auxiliary cooling components. This preventive check helps avoid future cooling-related issues.

Following your detailed explanation of the AC control unit issue and inspection recommendations, I better understand what to expect. Your experience with similar mileage really helps confirm my mechanic's initial suspicions about a sensor malfunction in the system. I will schedule the repair next week and request the additional checks you suggested, especially the wiring harness inspection and vacuum line examination. The complete vehicle maintenance checklist makes sense while everything is accessible. The temperature sensor readings have actually gotten more erratic this week, so timing seems right for the repair. I have noticed the engine cooling system still maintains normal operation, which aligns with your experience of it being a control unit communication issue rather than a mechanical cooling problem. Given the thorough diagnostic and repair process you outlined, the cost range seems justified. I will make sure they include the software update and sensor calibration as part of the service. Thanks for the detailed breakdown, it helps me go into the repair with clear expectations and knowledge of what needs checking.