BMW Z3 Fog Sensor Failure Causes Multiple System Issues

Hey there! I had nearly identical issues with my 2003 BMW Z4 last winter. The symptoms you're describing sound exactly like what I experienced, it turned out to be a faulty humidity sensor connection and corroded wiring harness near the rain sensor module. At the garage, they found that the main wiring connector had moisture damage, which was causing all those climate control problems. They had to replace the entire sensor unit and repair several connection points. While not a complex fix, it was definitely something that needed proper diagnostic equipment to pinpoint. The repair wasn't a major mechanical issue, but it's one of those things you want to fix before winter really sets in. Just make sure they check all the connected systems since these components are interlinked. In my case, they also discovered the drain channels needed cleaning to prevent future moisture problems. Hope this helps give you an idea of what you might be dealing with.

Thanks so much for sharing your experience, Glad to hear I'm not the only one who's dealt with this. Your Z4 issue sounds spot-on with what I'm experiencing. I'm feeling a bit more confident now about getting it fixed, especially knowing it's likely the humidity sensor and wiring. Would you mind sharing what the repair ended up costing you? Also curious if you've had any other related issues pop up since getting it fixed? Cheers!

Hey again! Great news, I wanted to follow up since I got the repair done. Just like my previous Z4 issue, it turned out to be pretty straightforward. The mechanic found a damaged cable connection at the fog sensor, exactly what I thought it might be based on the symptoms. The repair set me back 95 €, which honestly wasn't bad considering all the hassle these symptoms were causing. Everything's working perfectly now, no more foggy windows, the AC kicks in normally, and the mirror heating is back to life. Even those pesky washer nozzles are working great in cold weather. The best part? I haven't had a single problem since the fix, which was about three months ago. It's such a relief when these things turn out to be simpler than you fear, right? Just goes to show that finding a good mechanic who knows what they're looking for makes all the difference. Glad I could help out with your decision-making. Let me know if you need any other info!

Just wanted to give you an update, I took your advice and got my Z3 checked out today! You were absolutely right about finding a good mechanic. I found a specialist who really knew their BMWs, and they diagnosed it right away. Funny enough, my repair was even cheaper than yours, just 80 € for fixing a corroded wire and cleaning up the sensor connections. The mechanic was super transparent, showed me exactly what was wrong, and even gave me some tips to prevent future issues. The car's running like a dream now. AC's perfect, no more foggy windows, and everything's working exactly as it should. Such a relief to have it sorted before the weather gets worse! Thanks again for giving me the confidence to get it checked out, definitely saved me from a bigger headache down the road. Really appreciate all your help! Best wishes