BMW Z3 Climate Control Nightmare: Fogging & Heat Issues

Hi there! I have some experience working on BMWs and faced a similar issue with my 2003 BMW Z4 last winter. The symptoms were almost identical to what you're describing. After struggling with foggy windows and heating problems for a few weeks, I took it to my regular workshop. Turned out to be a faulty connection in the wiring harness going to the air distribution flap actuator. The mechanic found that the plug had corroded over time, causing intermittent connection issues. The fix wasn't too complicated, they replaced the wiring connector and cleaned the contact points. Total bill came to 95 Euro and it's been working perfectly since then. Before I can give more specific advice, could you tell me if you're getting any specific error codes on the display? Also, does the problem get worse when it's humid outside? This would help me understand if you're dealing with the exact same issue I had. By the way, have you had any other electrical issues with your Z3?

Thanks for sharing your experience! Actually, I'm getting error code E003 on the display, and yeah, it definitely gets worse in humid weather. The last time I had it serviced was around 145039 KM, and they didn't mention any electrical issues back then. Really helpful to know about the wiring harness, makes a lot of sense given the age of these cars. Haven't noticed any other electrical problems, but I'll keep an eye out. Maybe I should have my mechanic check those connections first before replacing any major parts. Sounds like a much cheaper fix than I was expecting!

Thanks for the follow-up! Yeah, that E003 code is exactly what I was getting on my Z4 too. When you mentioned it gets worse in humid weather, it really confirms my suspicion about the wiring harness being the culprit. In my case, the corrosion was pretty bad because moisture had been getting in there for who knows how long. I actually tried cleaning the connections myself first with some electrical contact cleaner, but it was only a temporary fix. The problem came back after a few days. Since your mileage is pretty similar to what mine was when I had the issue (I was around 150000 KM), I'd definitely recommend getting those connections checked first. Just make sure your mechanic thoroughly inspects the entire harness, not just the connector. Sometimes the corrosion can travel up the wiring. Quick tip: while they're in there, have them check the vacuum lines too. Mine had a small crack that wasn't causing problems yet, but could have been an issue down the road. Better to catch these things early, you know? Let me know how it goes. These old BMWs are great cars, but they do need some TLC with the electrical systems as they age!

Thanks so much for all the detailed advice! I really appreciate you sharing those extra tips about checking the vacuum lines too, definitely don't want any surprise issues popping up later. Just called my mechanic and scheduled an appointment for next week. Showed him your messages about the wiring harness and he agreed it's the most likely cause. Said he'll do a thorough check of all the connections and vacuum lines while he's at it. You're absolutely right about these BMWs needing extra care as they age. Still love my Z3 though, worth every bit of maintenance to keep it running smoothly. I'll keep you posted on what they find during the inspection. Thanks again for helping me avoid what could have been a much more expensive repair!