BMW Z4 Temperature System Total Failure, Fix Help?

As a 2009 BMW Z4 owner, I had almost identical issues last month. The temperature sensor wasn't the culprit in my case, it turned out to be a faulty wiring harness connection near the ECU. The symptoms matched yours exactly: dead temp readings, AC failure, and non-functioning mirror heaters. Had it fixed at a garage, the mechanic found corroded pins in the main connector that links these systems. They cleaned the connections and replaced a damaged section of the harness. While not a major repair in terms of components, it required careful diagnostic work to pinpoint the exact location of the fault. If you're facing similar symptoms, I'd suggest checking the wiring connections first before replacing any sensors. These electrical gremlins can be tricky, but once properly fixed, they shouldn't give you trouble again.

Thanks for sharing your experience! Good to hear you got it sorted. How much did the repair end up costing you? I was dreading a huge bill, so it's encouraging to hear it might just be a wiring issue rather than multiple sensor replacements. Has everything been working fine since the fix? I'm thinking of taking mine in next week, but wanted to have a rough idea of the costs before committing.

Hey there! Just wanted to follow up about the repair costs since you asked. After taking it to the mechanic last month, they found and fixed the outside temperature sensor fault, turned out it was just a damaged cable connection like I suspected. The whole thing set me back 95 Euro, which wasn't too bad considering all the symptoms it was causing. Everything's been working perfectly since the fix, the temperature display is showing correct readings, AC is blowing cold again, and those mirror heaters are back to normal. It's such a relief when these electrical issues turn out to be simpler than expected! Much better than having to replace multiple sensors or deal with more complex wiring harness issues like I initially feared. If you're still planning to get yours checked out, hopefully you'll have similar luck with a straightforward fix. These Z4s can be finicky with their electronics, but once you sort out the root cause, they're usually good to go.

Thanks for all the feedback! Just wanted to update, I finally got my car checked out. Man, what a relief! Took it to a different mechanic this time, and they were actually great. Found out it was just a loose connection in the wiring, plus a bit of corrosion they had to clean up. Only cost me about 120 bucks in total. The best part? Everything's working perfectly now. The temperature gauge is back to life, AC's blasting cold air like it should, and those mirror heaters are doing their job again. Such a weight off my shoulders, especially since I was worried it might be something major. Funny how sometimes the scariest car problems end up having the simplest fixes. Really glad I decided to get it sorted instead of putting it off. Lesson learned, don't wait around when these weird electrical issues pop up. Thanks again for pushing me to get it checked out!