VW Polo Heater Fault Linked to Solar Sensor Issue

I had a very similar issue with my 2017 VW Golf diesel last winter. As someone with moderate car repair experience, I can say that HVAC sensor problems can be tricky to diagnose correctly. The symptoms were identical, weak heating and an illuminated check engine light. The diagnostic scan pointed to a daylight sensor fault, which initially seemed unrelated to the heating problem. The sunlight sensor helps regulate the climate control system by measuring solar heat load, so a faulty connection can definitely cause heating issues. Took it to the workshop where they found the cable connection to the automotive sensor was damaged, causing intermittent communication errors. The repair involved replacing the wiring harness connector for the sensor. Total cost was 95€ and the heating worked perfectly afterwards. Before suggesting specific solutions, could you share: Have you noticed if the heating works better at night versus daytime? Did the fault detection system show any other codes besides the solar sensor? What trim level is your Polo (different HVAC configurations use different sensor setups)? These details would help determine if your issue matches what I experienced with my Golf.

Just had my latest service done at 137152km. Based on my diagnostic report, the sunlight sensor fault is triggering code P0513. The heating performance seems consistent regardless of day/night conditions. My HVAC sensor is showing inconsistent readings. The repair shop initially thought it might need sensor calibration but the issue persists. No other fault codes are showing up in the system. Did replacing the wiring harness completely resolve your temperature control issues? The 95€ repair cost sounds reasonable if it fixes both the sensor and heating problems.

Thanks for those additional details. Yes, replacing the wiring harness on my Golf completely resolved both the sensor issues and heating problems. However, given that your heating performance is consistent between day and night, your case might be slightly different from what I experienced. When my sunlight sensor was malfunctioning, the heating performance would vary noticeably between daytime and nighttime driving. Since yours remains consistently weak, there might be an additional issue beyond just the sensor wiring. The P0513 code combined with inconsistent HVAC sensor readings strongly suggests a fault detection problem in the sensor circuit. While the wiring harness replacement worked in my case, you might want the shop to check: 1. The sunlight sensor connector for corrosion 2. The entire sensor circuit pathway for potential breaks 3. The daylight sensor itself, as it might need replacement rather than just rewiring The repair cost could vary depending on whether you need just the wiring fix like I did (around 95€) or a complete solar sensor replacement (typically 150-200€). Given the symptoms, I would recommend having both checked thoroughly. The fact that sensor calibration didnt resolve the issue points toward a hardware problem rather than a software one, similar to what I dealt with.

My heating still isnt working properly. I took the car back to the shop and had them check all the items you suggested. The automotive sensor was indeed corroded, likely from water ingress near the windscreen. They replaced both the daylight sensor and the wiring harness for 185€ total. Unfortunately, while the check engine light is now off, the heating performance hasnt improved much. The temperature sensor readings are now stable according to the diagnostic tool, but the actual cabin temperature stays lukewarm at best. I guess the HVAC sensor wasnt the root cause after all. The mechanic is now suggesting checking the heater core and thermostat, which apparently will cost quite a bit more. Starting to think this might be a bigger job than initially hoped. Thanks for sharing your experience though, even if the final solution ends up being different, knowing about the sensor calibration and wiring issues helped rule those out as the main problem.