VW Fox electrical faults linked to rain-light sensor

Had similar sensor issues on a VW Polo 1.6 TDI (2008). The light sensor and rain sensor malfunctions were caused by bubbles forming under the gel pad where the sensor unit sits against the windshield. This led to false readings and multiple electrical faults, including unusual activation of lights and wipers. The issue requires removing the sensor unit, cleaning the old gel pad residue, and installing a new mounting pad with proper sensor calibration. If moisture gets between the sensor and windshield, it can trigger various electrical fault codes. Key findings from the repair: Rain sensor and light sensor share the same mounting unit, Faulty readings affect multiple systems including auto headlights and wiper control, The speedometer dimming uses input from the same light sensor, Complete sensor unit replacement isnt always necessary, Proper sensor calibration after remounting is crucial This was a serious issue that could affect safety systems, but the fix is straightforward for a shop familiar with car electronics. The repair involves specialized diagnostic equipment to reset the control modules and verify proper sensor operation after installation. Recommend finding a shop with experience in VW electrical systems since generic OBD readings wont show the full sensor communication data needed for proper diagnosis.

Thanks for sharing your experience. Dealing with similar headaches on my Fox 1.4 right now. The symptoms you described match exactly what I am seeing, unusual lights, dead wipers, and unresponsive controls. Your explanation about the gel pad makes perfect sense, especially since all these malfunctioning sensor issues started after a particularly hot summer. Just curious, do you remember roughly how much you paid for the repair? Also, has everything worked properly since the fix, or have you noticed any other car electronics acting up? I will definitely look for a shop that specializes in VW sensor calibration rather than going back to my regular mechanic who seemed lost with these electrical faults.

Just checked back on my Fox repair bill from last month, the full job came to 62€ to fix those annoying bubbles under the sensor gel pad. The rain-light sensor works perfectly now and hasnt shown any fault codes since. All the automatic functions are back to normal, wipers respond correctly to rain, headlights switch properly, and the dash dimming adjusts as it should. No more unusual light activation or electrical gremlins. The key was having a proper diagnostic reset after installing the new mounting pad. Really glad I went to a specialist who knew about these common sensor issues. They immediately recognized the problem with the gel pad and didnt waste time replacing parts unnecessarily. Having a shop familiar with car electronics diagnostics made all the difference in getting the auto sensor system working correctly again.

Thanks for the detailed responses. Finally got my Fox fixed yesterday! Found a specialist garage through a local VW forum and they nailed the diagnosis right away. Total bill came to 75€ which included fixing the rain sensor mount and recalibrating all systems. The tech showed me the old gel pad, it was completely dried out and cracked, just as mentioned here. They cleaned everything, fitted a new mounting pad, and ran full diagnostics on the car electronics. All the automatic functions are working perfectly now, no more ghost lights or dead wipers. Really glad I asked here first and learned about the gel pad issue. Saved me from paying for unnecessary sensor replacements. The car electronics are all back to normal and the rain detection works even better than before. Best part is knowing the electrical faults were just from a simple mounting problem rather than major sensor failure. Props to the shop for quick, honest work. If anyone else runs into similar auto sensor issues, definitely get it checked by someone who knows VW electronics.