Audi SQ5 Sunlight Sensor Causing Weak Heat Output

Had a similar issue with my 2018 Audi S4. The HVAC system showed weak performance due to a faulty solar sensor connection. The solar sensor helps regulate cabin temperature by measuring sunlight intensity and adjusting the climate control accordingly. The fault detection system revealed the sensor calibration was off due to a damaged wiring harness near the windshield. The temperature sensor readings were inconsistent, causing the climate control module to receive incorrect data. The repair involved replacing the wiring harness and recalibrating the automotive sensor system. While not a major mechanical issue, it required specialized diagnostic equipment to properly reset the HVAC control module. The job took about 3 hours at the shop. A worn cable connection can cause similar symptoms to a completely failed sensor, so its worth having the wiring checked before replacing the entire sensor unit. The SQ5 uses a complex network of sensors, and proper diagnosis is crucial to avoid unnecessary parts replacement. Based on these symptoms, recommend getting the sensor connections and wiring checked first, then moving to component replacement if needed.

Thanks for sharing your experience with the S4. I had almost identical issues with my SQ5 last winter. The daylight sensor was misreading and causing temperature regulation problems. After inspection, they found corroded wiring leading to the sunlight sensor cluster near the windshield. Did you ever find out the total repair cost? Just wondering how it compares, as I ended up paying around 450 Euro for the complete fix including sensor calibration and new wiring. Also curious if youve had any other HVAC sensor problems since the repair?

The sunlight sensor issue was completely resolved after fixing the cable connection, which only cost 95 Euro. Much better than a full sensor replacement. The repair shop identified the root cause quickly, just a faulty plug connection to the daylight sensor that was causing irregular HVAC system behavior. The fault detection system now shows no errors, and the climate control works flawlessly. The temperature regulation has been spot-on since the repair, with the automotive sensor properly measuring sunlight intensity to adjust cabin comfort. Your repair cost seems high in comparison, but that makes sense if they replaced wiring and did a full sensor calibration. Sometimes these HVAC sensor problems can be fixed with simpler solutions if caught early. No other sensor-related issues have occurred in the past year. The climate control system maintains consistent performance regardless of external light conditions, which confirms the sunlight sensor is functioning correctly.

Thank you for everyone's input. Just wanted to update on my SQ5 situation after visiting a different mechanic last week. Turns out my daylight sensor wasnt the main culprit, they found a rodent had chewed through some of the HVAC wiring harness. The mechanic showed me where the temperature sensor wiring was damaged, along with several other connections. The entire repair including parts and labor came to 280 Euro, much less than the 450 Euro quote from the first shop that blamed it on the sunlight sensor. The heating now works perfectly and all error codes are cleared. Really glad I got that second opinion instead of replacing the automotive sensor system unnecessarily. The new shop even cleaned and protected the wiring against future rodent damage at no extra cost. Lesson learned, always worth getting multiple opinions when dealing with sensor fault issues, as the root cause isnt always what it seems.