BMW Temp Sensor Failure Kills AC and Mirror Functions

I had nearly identical issues with my 2005 BMW 3 series last year. The symptoms were exactly what you're describing, temp display malfunction, AC problems, and mirror heater failure. In my case, it turned out to be a damaged wiring harness causing poor connections to the ambient air temperature sensor. The garage found several frayed wires near the front bumper area where the sensor connects. They had to replace the wiring harness and the sensor unit itself. It wasn't a major mechanical issue, but it did affect multiple systems since these components are interconnected. The repair took about half a day. I'd definitely recommend getting it checked soon since it impacts your AC system. Just make sure your mechanic properly tests all the connections before replacing parts. Sometimes it's just a loose connection rather than a failed sensor.

Thanks for sharing that info about the wiring harness! I've been worried about taking it to another shop, but hearing your experience makes me feel better about getting it fixed. Can't remember if you mentioned, how much did the repair set you back? And has everything been working properly since they fixed it, or have you noticed any other quirks pop up?

Hey there! Glad to give you an update on my situation. After I got it fixed last year, everything's been working perfectly fine, no more temperature display issues, AC works great, and those mirror heaters are doing their job again. Since you asked about the cost, my repair bill came to 95 € for fixing the cable connection that was acting up. Honestly, it was cheaper than I initially feared it might be! The mechanic found it was just a faulty connection at the sensor plug, not the entire wiring harness like they first suspected. Much simpler fix than expected. No other issues have popped up related to this at all. The outside temperature sensor's been spot-on ever since the repair. Was definitely worth getting it sorted, made such a difference having all those systems working properly again. Sometimes the simple fixes are all you need! Don't hesitate to take it in, these sensor problems can be pretty straightforward once a good mechanic takes a look. Fingers crossed yours turns out to be a simple fix too!

Thanks so much for the detailed follow-up! You really helped me make a decision. I finally took my BMW to a different mechanic today, and guess what? It was almost exactly what you described, just a loose connection at the sensor plug causing all those problems. The repair only took about two hours and cost me way less than I was expecting. The mechanic showed me where the wiring was loose and fixed it right up. Now my temperature display is working perfectly, the AC is blowing cold air again, and those mirror heaters are back in action. I'm actually pretty relieved I didn't wait any longer to get it checked out. Was kicking myself for being so nervous about finding a new mechanic. Sometimes you just need that little push from someone who's been through the same thing! Really appreciate you taking the time to share your experience, saved me a lot of worry and probably some money too. Finally feels good to have everything working properly again. Thanks again for the help!