RS6 Light Switch Malfunction Causes Random Activation

Last month my 2017 RS4 had nearly identical symptoms with the headlights turning on out of nowhere. The diagnostics revealed a faulty dimmer switch connection in the main automotive switch unit. The root cause was corroded terminals inside the switch assembly, affecting multiple lighting circuits including the tail lights. The fix required complete replacement of the switch unit since cleaning the contacts provided only temporary relief. This is actually a known weak point in these models after they pass 150000 KM. The connector pins can develop resistance over time due to thermal cycling. While not a safety-critical fault, it definitely needs proper attention since it can drain the battery if left unchecked. The repair process is straightforward but requires specific diagnostic equipment to properly code the new switch unit to the vehicle. Would strongly recommend having a certified shop handle this repair. They will need to: Verify fault codes related to the lighting system, Test switch unit resistance values, Replace complete switch assembly if values are out of spec, Code new unit to vehicle systems, Clear all related fault codes The job itself takes about 2 hours when done properly. This is not a DIY-friendly repair due to the programming requirements.

Thanks for sharing your experience with the headlight switch issue. That matches exactly what I was seeing with my RS6 electrical problem. Got it fixed about 6 months ago and the new automotive switch unit has been working perfectly since then. The tail lights are also behaving normally now. Just wondering, do you remember roughly what the total repair cost was for your fix? And has everything stayed working properly since the repair? I paid around 450 Euro for parts and labor but curious if that was in line with what others experienced.

Had similar concerns about the repair cost initially. However, my recent visit to the mechanic confirmed it was just a faulty connection in the headlight switch assembly, much simpler than a full unit replacement. Only paid 95 Euro to fix the defective cable and clean the connector plugs. The electrical problem was resolved completely. The fuse box and all related components were inspected as well, but everything else tested fine. Really glad it turned out to be just a connection issue rather than needing the entire automotive switch unit replaced like yours did. That explains the big difference in repair costs between our cases. Going on 3 weeks now since the fix and the lighting system has been working flawlessly. No more unusual headlight activations or error codes. Sometimes these car switch problems can be resolved with basic electrical repairs rather than full component replacement.

Had my RS6 fixed last week after dealing with the same lighting system troubles. Took it to my regular mechanic who diagnosed it as a complete failure of the dimmer switch assembly, exactly what you experienced. The headlight switch was totally shot and needed full replacement. The repair ended up costing 450 Euro which covered both parts and labor. The automotive switch unit replacement took about 2.5 hours since they had to reprogram everything. Now all the car lighting functions work perfectly, no more unusual activations or error messages. Really glad I got it properly diagnosed this time. My previous mechanic just cleaned the connections which only fixed things temporarily. The fuse box inspection showed everything else was fine, so replacing the main switch assembly was definitely the right call. Just wanted to close the loop and confirm your diagnosis was spot-on. Thanks for helping me avoid another failed repair attempt.