BMW M4 Window Heating Failure: Owner Seeks Fix & Cost Tips

I had a similar issue with my 2016 BMW M3 last winter. When both front and rear window heating failed, I got the "Battery heavily discharged" warning. Initially thought it was just a battery problem, but my mechanic found that the voltage regulator was failing, causing irregular power distribution to the heating elements. The alternator wasn't charging the battery properly, which affected all electrical systems, including the heaters. Had to get the voltage regulator replaced and install a new battery since the old one was damaged from multiple discharge cycles. It was a serious repair job because they had to access several components behind the engine bay. The heating worked perfectly after fixing these electrical issues. If you're seeing similar symptoms, I'd recommend getting the electrical system checked first before replacing any heating elements. Just make sure they test both the alternator and battery health.

Thanks for sharing your experience! That's really helpful as I'm seeing very similar symptoms. You've described exactly what I suspected might be happening with my M4. Honestly, I was worried it might be something even more complex. Did you remember roughly how much you ended up paying for the whole repair? Also, curious if you've had any other electrical gremlins pop up since getting it fixed?

Hey there! Glad I could help with your M4 situation. Just wanted to update you on the costs since you asked, the whole thing set me back 290 € for the battery and electrical work. The good news is the rear window heating's working perfectly now! It's such a relief not having to deal with foggy windows anymore. As for other electrical issues, nope, haven't seen any gremlins since getting it sorted. The car's been running like a charm. Honestly, once they fixed the voltage regulator and put in the new battery, all those electrical quirks disappeared. The M3's been super reliable on that front. Just keep in mind that these performance cars can be a bit sensitive when it comes to electrical systems. Getting it fixed by someone who really knows BMWs is worth every penny, saves you from bigger headaches down the road. If you're still shopping around for a mechanic, make sure they do a proper diagnostic on both the alternator and battery before jumping to conclusions.

Thanks for the detailed information! I wanted to let you know that I finally took my M4 to the mechanic yesterday. The funny thing is, they found exactly what you described, a failing voltage regulator and a weak battery. The mechanic showed me how the alternator wasn't charging properly, which explained all those heating issues. I ended up getting both parts replaced, and it cost me around 320, a bit more than what you paid, but still reasonable considering the work involved. The best part is that both front and rear heating are working perfectly now. It's amazing how quickly they diagnosed and fixed it. The mechanic I found was actually pretty honest, explained everything clearly and even showed me the worn-out parts. Such a relief after my previous bad experiences. Really appreciate your help in pointing me in the right direction. The car's running great now, and hopefully, I won't have to deal with any more electrical problems!