BMW Z4 A/C Complete Failure, Compressor Issues & Solutions

Hey there! I've got some experience with car repairs. Had a similar issue with my 2011 BMW M3 last summer. The A/C completely died, and like yours, wouldn't turn on at all. After getting the codes read, my trusted mechanic found it was an undervoltage problem affecting the A/C compressor system. The fix wasn't too complex but definitely needed professional hands. My mechanic replaced some electrical components and recalibrated the system. Total bill came to about 240 Euro, but it was worth it, A/C's been working perfectly since then. Could you share what specific error codes you're getting? Also, before the A/C completely stopped, did you notice any weird noises or inconsistent cooling? This info would help compare if it's the same issue I faced with my M3. From my limited experience, BMW's A/C issues are often electrical rather than mechanical, but it's best to get it properly diagnosed. Would definitely recommend getting it checked soon before summer hits!

Thanks for sharing your experience! My Z4 actually just had its latest service done about 2 months ago, and I'm currently at 109396 KM. The error codes I'm getting are P0645 and P0747. Before it completely stopped working, I did notice the A/C would occasionally make a slight clicking sound when turning it on, but I didn't think much of it at the time. No strange noises from the compressor though. What's interesting is that my temperature gauge is working fine, and the fan still blows, just no cold air at all. Did you notice anything similar with yours before the complete failure? I'm hoping it's just an electrical issue like yours was, but I'm a bit worried it might be the compressor itself.

Oh hey, thanks for those details! Yeah, those error codes definitely ring a bell, especially that P0645. When I had my M3's A/C issues, I was getting similar codes. The clicking sound you mentioned is super familiar too. In my case, it started with those occasional clicks, then progressed to complete failure. My car was around 98000 KM when it happened, also not long after a service, which was pretty frustrating. The symptoms were exactly the same, fan working, temperature controls responding, but absolutely no cold air. Just like you're experiencing now. Initially, I was worried sick it was the compressor too (which would've been way more expensive), but turns out it was the A/C compressor clutch relay and a faulty control module. The clicking was actually the relay trying but failing to engage the compressor. Based on what you're describing, it sounds remarkably similar to what I dealt with. The good news is, if it's the same issue, it's more of an electrical fix than a mechanical one. My advice would be to get it checked soon though, driving around without A/C is no fun, and these issues tend to get worse if left unchecked. When you do take it in, make sure they check the electrical system first before jumping to conclusions about the compressor. Could save you some serious cash!

Thanks so much for the detailed info! That's honestly a huge relief to hear that your issue was just the relay and control module rather than the whole compressor. The similarities between our problems are really striking, especially that clicking sound and the error codes. I've been stressing about potentially needing a full compressor replacement, but your experience gives me hope it might be something simpler. I'll definitely take your advice and ask them to check the electrical system first, focusing on the relay and control module. Think I'll book it in next week. Really appreciate you sharing your experience, it's super helpful to know what to expect and what to ask the mechanic to look at. I'll update the thread once I get it sorted out in case anyone else runs into similar issues with their BMW!