BMW 3 Series Cold Start Woes: PTC Heater Investigation

Had the same issue with my 2020 BMW 4 Series last winter. Electric auxiliary heater went completely bad. Symptoms matched yours exactly, slow warm-up, rough cold starts, and higher fuel consumption. My mechanic found that the PTC heating element was defective and also damaged the wiring harness connected to it. Had to replace both components. It was quite serious since the faulty heater was causing the engine management system to compensate incorrectly, leading to those rough starts and fuel economy issues. The repair wasn't just a quick fix, needed specialized diagnostic equipment to properly calibrate the new heater system after installation. Took about two days at the garage, but solved all the problems. Engine now warms up normally, runs smooth from cold starts, and fuel consumption is back to normal. If you're seeing similar symptoms, would definitely recommend getting it checked soon. These issues tend to get worse and could potentially affect other systems if left unchecked.

Thanks for sharing your experience! I'm dealing with these exact symptoms right now and it's really helpful to know I'm not alone with this. Yours sounds like it was quite a complex repair job with both the PTC element and wiring harness needing replacement. Do you remember roughly how much you ended up paying for everything? Also, has everything been running smoothly since the repair, or have you noticed any other issues pop up?

Hey there! Glad I could help with my previous reply. I actually just got my car back from the mechanic last week, they fixed exactly what we were talking about. The total bill came to 350 € for replacing the defective electric auxiliary heater, and I couldn't be happier with the results. Since the repair, my car's running like a dream, no more of those annoying cold start issues or excessive fuel consumption problems. The engine warms up properly now, and everything's working exactly as it should. It's such a relief to have it sorted out! I've put about 500 km on it since the fix, and there haven't been any new issues popping up. The mechanic did a thorough job with the diagnostics and calibration, which I think really made the difference. Honestly, it was worth every cent to get it properly fixed rather than letting it get worse. If you're still experiencing those symptoms, I'd definitely recommend getting it checked out sooner rather than later. The peace of mind alone is worth it, and you'll likely save money on fuel in the long run too.

Thanks so much for the detailed follow-up! Just got back from the mechanic myself, and you won't believe it, I actually had the same issue with my PTC heater. Finally decided to take it in after our chat, and I'm really glad I did. The whole process was quite an experience. My mechanic found that the heater unit was completely shot and needed full replacement. It hurt my wallet a bit more than yours, ended up costing me about 450 € with labor, but honestly, it's been worth every penny. The difference in how my car runs now is like night and day. No more sluggish cold starts, the engine warms up properly, and my fuel consumption has dropped back to normal. Can't believe I put up with those issues for so long! Really appreciate you sharing your experience, it gave me the push I needed to get this sorted. Now I can stop worrying every time I start the car on a cold morning!