VW Up Sunlight Sensor Causing Heat System Malfunction

I had a similar solar sensor issue with my 2013 VW Polo. As someone with moderate experience working on VWs, I can share what happened with my car. The symptoms matched yours exactly, inconsistent heating output and error codes related to the sensor system. After some basic troubleshooting, I took it to my regular workshop where they diagnosed a faulty connection in the daylight sensor wiring harness. The cables had worn through due to normal wear and tear, causing intermittent sensor fault readings. The repair involved replacing the damaged wiring and connectors near the automotive sensor unit. Total cost was 95€ including diagnostics and parts. Since the fix, the heating system has worked flawlessly. To better assist with your specific case, could you share: Does the error code appear consistently or intermittently? Have you noticed if the heating issues vary depending on outside temperature? Are there any other electronic systems showing unusual behavior? Can you provide the specific error code being displayed? This information would help determine if your car sensor issue matches what I experienced or points to a different underlying problem.

Last service was done at 90000km and the HVAC sensor issue started shortly after. The fault detection system keeps showing the error consistently now, not just occasionally like before. The heating problems happen regardless of outside conditions. The error code is P0073 which confirms it is linked to the solar sensor. No other electronic systems are affected. I will get it checked at a workshop based on your feedback since the symptoms match exactly what you described. The wiring harness issue seems a plausible cause given the mileage and age of my Up. Thanks for sharing your specific repair experience.

Thanks for providing those additional details, this really helps confirm my initial suspicion about your HVAC sensor problem. The consistent P0073 code and timing after the service actually mirrors exactly what happened with my Polo. Just like your case, my solar sensor issues emerged shortly after routine maintenance. The fact that your heating problems persist regardless of conditions strongly suggests a wiring fault rather than the sensor itself being defective. A key point: when the workshop repaired my wiring harness, they found the service work had actually contributed to the problem. The sunlight sensor connections had been disturbed during maintenance, accelerating the wear on already aging wires. My total repair time was about 2 hours, and sensor calibration was required after the new wiring was installed. The workshop also applied protective covering to prevent future wire chafing, which I highly recommend requesting. Since your symptoms are identical and the error code matches, having the wiring harness inspected should be your first diagnostic step. Be sure to mention the recent service timing to the technician, it could help pinpoint the issue faster. Would you mind updating the forum once you get it checked? Your feedback could help others with similar car sensor problems.

The symptoms you've described and your repair experience match my situation perfectly. The consistent P0073 error code points exactly to the solar sensor issue you encountered. Given that my HVAC sensor problems also started right after maintenance, the damaged wiring harness theory makes complete sense. I will specifically ask the workshop to inspect the wiring connections around the daylight sensor, especially since the timing after service matches your case. Good to know about the 2-hour repair time and the need for sensor calibration afterward. I will make sure they add protective covering to prevent future wire damage. Will schedule the repair next week and post an update here about what they find. The details about your repair costs and process are really helpful for setting expectations. Since all the symptoms align, the error codes, timing after service, and the constant heating issues, I feel much more confident about getting this resolved. Thanks for the thorough explanation.