BMW M3 Seat Heater Failure, Common Fix & Diagnosis

Hey there! I had a similar issue with my 2009 BMW M5 last winter. I have some experience working on cars, mostly basic maintenance and diagnostics. The symptoms were exactly like yours, the seat heater would either not work at all or cut out seconds after turning it on. Took it to my trusted workshop and they found a faulty heating mat in the driver's seat. The whole repair, including labor, set me back about 390 Euro, but it's been working perfectly since then. Before you head to the shop, could you share if this happens on both seats or just one? Also, have you noticed any tears or wet spots on the seat that might have damaged the heating elements? If you want, I can ask my who owns a 2008 M3 if he's encountered anything similar with his car. Just let me know!

Thanks for the detailed response! Mine's acting up on the driver's side only, and the seat is in great condition with no visible damage. My M3 just hit 73655 KM and had its last service about 2 months ago, but this wasn't checked then. It's good to know about the heating mat being the culprit in your case. That repair cost seems reasonable compared to what I was worried it might be. I'm hoping it's the same issue and not something more complex with the wiring or control module. I'll definitely get it checked out soon before winter hits. Did your mechanic mention how long the repair took?

Hey again! Thanks for following up. Yeah, as I mentioned, my M5 had almost the exact same symptoms. Since you asked, the repair took about 3-4 hours at my workshop. They had to remove the seat cover carefully to access the heating mat, it's quite a delicate job because you don't want to damage the leather or the electrical connections. Given that your issue is also only on the driver's side and the seat's in good condition, I'm pretty confident it's the same problem I had. The mileage on your M3 is actually pretty similar to what mine had when the heater failed. These heating mats tend to wear out from all the getting in and out of the car. Just a heads up, make sure they check all the connections while they're in there. My mechanic found a slightly loose connector when he was replacing my heating mat, so he fixed that too at no extra cost. The whole system's been working perfectly for almost a year now. Let me know how it goes when you get it fixed! Always good to compare notes on these things, especially with these performance BMWs.

Thanks so much for all this info! Really helpful to know about the repair time and that they should check the connections too. I'll definitely mention that when I take it in. Actually just called my local BMW specialist and booked it for next week. Knowing it's likely just the heating mat is a huge relief, I was worried it might be something major with the electrical system. Makes total sense about the wear and tear from getting in and out of the car. I'll definitely update you once it's fixed. Really appreciate you taking the time to share your experience, it's exactly the kind of firsthand info I was hoping to get before heading to the shop. These M3s might be amazing machines, but they sure can throw some interesting problems our way!