BMW X3 AC Dead: Heat Exchanger Sensor Malfunction?

Hey there! I had a similar issue with my 2007 BMW X5 3.0i last summer. The symptoms were exactly the same, complete AC failure and dead climate control panel. Initially thought it was just a sensor, but turned out the AC control unit itself was defective. Took it to the garage and they found that moisture had damaged the control module's circuit board. It wasn't a quick fix, they had to replace the entire climate control unit. The repair took about 4-5 hours because they needed to remove parts of the dashboard to access the unit. It was definitely a serious issue since the car was basically undriveable in warm weather. The new control unit resolved all the problems, AC, temperature regulation, and fan speeds all worked perfectly after that. My advice: Make sure they properly diagnose the issue before replacing parts. In these BMWs, the temp sensor isn't always the culprit even when the scan suggests it. Get them to check the control unit's connections and circuit board first. Hope this helps.

Thanks for sharing your experience! That's really helpful as it sounds very similar to what I'm dealing with. Good to know about the control unit potentially being the real problem rather than just the sensor. Would you mind sharing how much you ended up paying for the whole repair? Also curious if you've had any other AC-related issues pop up since getting it fixed?

Hey again! Happy to give you an update! After taking it to the mechanic, they found both issues, the temperature sensor in the heat exchanger was indeed faulty, but just like I suspected, the AC control unit was also shot. They fixed both problems, and it set me back 980 € for the control unit replacement. The sensor repair was covered under an extended warranty I had, which was a nice bonus! Since getting it fixed last summer, my X5's climate control system has been working like a charm. No more error messages, the AC blows nice and cold, and all the automatic controls work perfectly. It was definitely worth getting both issues sorted properly rather than just addressing the sensor problem alone. If you do get yours fixed, make sure they check both components thoroughly. These BMWs can be tricky, and sometimes one problem masks another. I've had zero AC issues since the repair, it's running just as good as new. Let me know if you need any other details about the repair. Always happy to help a fellow BMW owner!

Thanks a million for all the details! I finally got mine fixed yesterday, and boy, what a journey it was! The mechanic I found was actually really thorough, spent a good hour just diagnosing everything before starting the work. Turns out you were spot on, both the sensor and control unit needed replacing. The whole thing cost me quite a bit, but honestly, it was worth every penny. The AC's working perfectly now, no more error messages, and the climate control system's back to life. The mechanic even showed me the old control unit, it was pretty damaged from moisture, just like yours was. Really appreciate you sharing your experience, it helped me know exactly what to expect and what to ask the mechanic to check. Feels great to have a properly working AC system again! Thanks again for all your help!