BMW M4 AC Failure: Common Compressor Issues Explained

Hey there! I had a pretty similar issue with my 2014 BMW M3 last summer. I've got some experience working on cars, but electrical stuff isn't really my forte. My AC completely died too, and after taking it to my trusted workshop, they found it was an undervoltage problem that was causing the AC compressor to shut off as a safety measure. They had to replace some electrical components and recalibrate the system. The whole thing cost me about 240 Euro, but it's been working perfectly since then. Before you jump to conclusions though, could you share what specific error codes you're getting? Also, does your AC make any unusual sounds when you try to turn it on? Knowing these details would help me tell if you're dealing with the same problem I had. BMWs can be tricky with electrical issues, so it's better to be sure.

Thanks for sharing your experience! My M4 actually isn't making any sounds when I try to turn on the AC. Last service was done 3 months ago at 84,533 km, and everything was working fine until yesterday. I'm getting error codes P0645 and P0562, which seem to point towards an electrical issue like yours. Did your AC also go completely silent before it stopped working? Just trying to figure out if I'm looking at a similar fix or if it might be something different. It's pretty frustrating since the weather's getting warmer now.

Hey again! Yes, my M3 also went completely silent before the AC stopped working, it was exactly like what you're describing. Those error codes you mentioned (P0645 and P0562) are exactly what I had too, which pretty much confirms we're dealing with the same issue. It's definitely an electrical problem affecting the AC compressor control circuit and system voltage. Just to give you more details about my experience, before it went completely silent, I did notice that my AC was slightly less effective for about a week, but I didn't think much of it at the time. The undervoltage issue basically triggers the car's fail-safe mode to protect the compressor from damage. The good news is that since you caught it early like I did, there's probably no damage to the actual compressor. In my case, they had to replace the AC relay and a voltage regulator, then recalibrate the whole system. The repair wasn't too complicated, and the car was ready the same day. Given that you're getting the same symptoms and error codes, I'd bet you're looking at a similar repair cost to what I paid. Just make sure they check the entire electrical circuit while they're at it, these problems sometimes come back if they only fix the immediate issue without checking the whole system.

Thanks so much for the detailed explanation! That's actually really reassuring to hear that your situation was so similar to mine. It's good to know it wasn't a massive repair job either. I think I'll book it in at the workshop tomorrow, doesn't sound like something I want to leave too long, especially with these specific error codes. The fact that yours was fixed in a day and has been working fine since is exactly what I needed to hear. Really appreciate you taking the time to share all those details about the relay and voltage regulator too. At least now I won't be completely in the dark when talking to the mechanics! I'll follow up here once it's fixed to let others know how it went. Thanks again for your help!