Audi S5 Multiple System Failures Traced to Humidity Sensor

I had a similar issue with my 2014 Audi S4 last winter. Having some experience with sensor malfunctions, I recognized the pattern of multiple climate control features failing at once. The automotive sensor system was giving error codes similar to yours. Initially thought it was the humidity sensor itself, but the workshop diagnostic revealed it was actually a damaged cable connection to the sensor unit. The visibility and climate control systems are interconnected through this wiring harness. The fix involved replacing the corroded plug connection and performing a sensor calibration. Total repair cost was 95 Euro, which was less than expected since no actual sensor replacement was needed. Before suggesting specific solutions for your S5, could you: Share the exact error code displayed, Confirm if these issues started gradually or all at once, Mention if you notice these problems more during specific weather conditions, Check if the windshield defrost function still works properly The S4 and S5 share similar sensor architecture, but knowing these details would help determine if your malfunction has the same root cause as mine.

Thanks for the insights. Last service was at 141176 KM, and the dashboard warning light just started flashing today. The error code is U112200. All functions stopped working simultaneously during heavy rain last week. And yes, the windshield defrost function is completely dead too. Looking at the service manual, there might be a direct connection between the climate control unit and the humidity sensor circuit, both using the same wiring harness that runs behind the dashboard. The malfunction seems more severe when temperatures drop below freezing. Will get it checked at the shop but wanted to verify if a full sensor replacement is really needed since these units are quite expensive.

Thanks for providing those additional details. The simultaneous failure during heavy rain and the U112200 error code on your S5 matches exactly what I experienced with my S4 before the repair. The windshield fogging issues and complete failure of the defrost function strongly point to a wiring problem rather than a failed humidity sensor unit. In my case, water intrusion through a deteriorated grommet caused corrosion in the main connector, triggering the electrical issue across multiple systems. Since your problems started during rain and worsen in cold conditions, I suggest having the shop check: 1. The wiring harness behind the upper dashboard area 2. The connector seals around the humidity sensor 3. The ground connection points for the climate control module A full sensor replacement would cost around 400 Euro plus labor, but if your issue mirrors mine, you might only need the wiring repair which typically runs 100-150 Euro including diagnostic time. Would definitely have them run a complete electrical diagnostic before changing any parts. The dashboard warning symptoms and timing of the failure sound identical to what I dealt with.

The wiring harness explanation makes perfect sense, especially since all these issues started during that rainstorm. This could save me a lot of money if its just a connection problem rather than a complete sensor failure. My windshield fogging has gotten worse this week, which fits with your water intrusion theory. The climate control system is completely unresponsive now, and the dashboard warning keeps flashing even after clearing the U112200 code. Made an appointment with the shop for tomorrow. Will have them focus on checking the wiring and connectors first before replacing the humidity sensor. Really hope its just corrosion in the main connector like in your case. The 150 Euro repair cost sounds much better than 400 Euro for a new sensor unit. Will update once I get the diagnostic results and know exactly what needs fixing. The sensor calibration requirement you mentioned is good to know about too, will make sure they include that in the repair if needed.