BMW 5 Series AC Failure: Temp Sensor or Control Unit?

I had a similar issue with my 2016 BMW 3 Series last summer. The symptoms were almost identical to what you're describing. After taking it to the garage, they found it was indeed a faulty connection in the wiring harness between the climate control module and the temperature sensor. It turned out the wire insulation had worn down over time, causing intermittent connection issues. The repair involved replacing the wiring harness and recalibrating the climate control system. The work took about 4-5 hours, and while not cheap, it wasn't as serious as I initially feared. My advice would be to get it checked soon though, in my case, delaying the repair could have led to more extensive damage to the climate control module itself. The symptoms started just like yours, error messages, inconsistent temperature control, and the AC refusing to engage. Not a DIY job unless you've got diagnostic equipment and experience with BMW electrical systems.

Thanks for sharing your experience, really helps! The wiring harness issue sounds exactly like what I'm dealing with. How much did you end up paying for the whole repair job? Also curious if you've had any other AC problems since getting it fixed?

Hey again! Good news, I was just coming back to update you. I actually got my car fixed last week, and you were spot on about the temp sensor. Turned out it was exactly what I had suspected, a faulty interior temperature sensor caused by a bad cable connection. The mechanic sorted it right out and it was way cheaper than I expected, only 95 € to fix the cable connection. Much better than having to replace the entire system! I'm happy to report I haven't had any issues since the repair. The AC's working perfectly now, no more error messages, and the temperature control is back to normal. Everything's running smooth as butter. It's such a relief because I was worried it might be something more serious (and expensive!). Just goes to show sometimes these issues aren't as bad as they seem. If your symptoms are similar to what mine were, you might be looking at the same relatively simple fix. Best of luck with yours, let me know how it turns out!

What a relief! Just got back from my mechanic today and wanted to give you guys an update. Took your advice and got it checked out right away. The diagnosis was pretty quick, turned out to be a combination of a worn-out wiring harness and a failing temperature sensor, just like you mentioned. Total bill came to about 300 bucks, more than your repair but still way better than I'd feared. The mechanic showed me the old parts, and those wires were definitely shot! He got everything fixed up in about three hours. Best part? The AC's working perfectly now, blowing nice cold air, and all those annoying error messages are gone. Really glad I asked here before going in blind. You guys saved me from probably getting overcharged somewhere else. The car's running great now, and with summer coming up, this couldn't have worked out better. Thanks again for all the help!