BMW Z3 Cold Start Issues: PTC Heater Problems?

Hi there! I had a similar issue with my 1999 BMW M3 last winter. I have some basic car maintenance experience, but heating systems aren't my forte. My car showed pretty much identical symptoms, slow warm-up, rough idle when cold, and higher fuel consumption. After getting tired of freezing during my morning drives, I took it to my regular workshop. They diagnosed a faulty electric auxiliary heater. The repair set me back about 350 Euro, but it fixed all those issues completely. Before suggesting anything specific for your Z3, could you share: Are you getting any specific error codes with that check engine light? When did you first notice these symptoms? Have you had any recent work done on the heating system? BTW, worth checking if there's a recall or TSB for your specific model year, BMWs sometimes had heating system campaigns.

Thanks for your detailed response! In my Z3 (53694 KM), the check engine light shows code P0128, pointing to a low coolant temperature. Haven't had any heating system work done in recent times, and these issues started about three weeks ago when the weather got colder. Just had my regular service last month, everything else seemed fine then. Your experience with the electric auxiliary heater sounds quite similar to what I'm dealing with, especially the rough idle and fuel consumption issues. Might have to bite the bullet and get it checked by a pro like you did.

Hey again! Thanks for providing those details about your Z3. You know, after seeing your error code P0128, I'm even more convinced it's similar to what I dealt with on my M3. When I had the issue, the first cold morning I noticed it, my fuel consumption shot up by about 15%. The engine management was probably trying to compensate for the low temp readings by running rich. My mechanic explained that the electric auxiliary heater helps the engine reach optimal operating temperature faster, especially in cold weather. When it fails, everything goes a bit haywire. Since your symptoms started with the cold weather and you're getting that specific code, it really does sound like the same problem. My repair included replacing the auxiliary heater unit and checking the connections. The difference in performance was like night and day, warm-up time went back to normal (about 5-7 minutes), and the rough idle completely disappeared. Given your relatively low mileage, it might seem early for this kind of issue, but these heaters can fail regardless of mileage. Mine had about 78000 KM when it went bad. If you decide to get it checked, make sure they look at the wiring too, sometimes it's not just the heater unit itself but also corroded connections. Want me to share what specific tests my mechanic ran to confirm it was the heater? Might help you avoid paying for unnecessary diagnostics.

Thanks so much for the follow-up! That's super helpful, especially knowing about your fuel consumption increase, mine's gone up about the same percentage. You're probably right about the engine running rich to compensate. I'd definitely appreciate knowing what tests your mechanic ran. Honestly, it's reassuring to hear that your repair made such a clear difference. My Z3's mileage is indeed lower, but given its age (22 years), I guess these things are bound to happen regardless of kilometers driven. I'll get it booked in next week. Really hoping it's just the heater unit and not anything more complex. The rough idle is driving me crazy, especially since I know the car can run so much smoother. I'll make sure to ask them to check those wiring connections you mentioned too, that's a great tip I wouldn't have thought about. Thanks again for sharing your experience. It's really helped me understand what I might be dealing with!