BMW Z4 Heat System Failure: Quick Diagnostic Help Needed

Hey there! I had a similar issue with my 2008 BMW Z4 sDrive35i last winter. The symptoms you're describing sound exactly like what I experienced. In my case, it turned out to be more than just the water valve, there was a wiring harness problem where the cable connection to the heater control valve was damaged. The mechanic found that some of the wires had corroded and weren't sending proper signals to the valve. It was actually pretty serious because the faulty connection was causing the system to work intermittently, which could have led to bigger problems with the heating system if left unchecked. The repair involved replacing the wiring harness and the heater control valve. The work took about a day at the shop. While it wasn't a quick fix, it completely resolved the uneven heating issues and cleared all the error codes. Best to get it checked soon, electrical issues with heating systems usually don't fix themselves and tend to get worse over time.

Thanks for sharing your experience! That's really helpful. My symptoms sound pretty much identical to what you had. I'm gonna have it checked out asap since you mentioned it could lead to bigger problems. By the way, do you remember roughly how much you paid for the whole repair? Also, has everything been working fine since then, or have you noticed any other heating-related issues?

Hey again! Happy to tell you that since having it fixed, my Z4's heating has been working perfectly, no issues whatsoever! The repair was definitely worth every penny. Speaking of which, I actually came out pretty lucky compared to what I initially feared, it cost me 95 € to fix the cable connection issue. The mechanic found that the water valve was indeed defective, but once they sorted that out and fixed the faulty wiring connection, everything's been running like a charm. I've put quite a few miles on the car since then and the heating's been super consistent, no more of that annoying uneven heat distribution we were dealing with before. The error codes haven't come back either, which is always a good sign! Just make sure you get it looked at by someone who really knows BMWs, they can be a bit tricky with these kinds of electrical gremlins. But once it's properly fixed, you should be good to go!

Thanks so much for the detailed follow-up! I just got back from the mechanic today, and boy, what a journey that was! Turned out my issue was pretty similar to yours, but with a twist. The main problem was indeed the wiring, but they also found some gunk buildup in the heating system that needed cleaning. I was really nervous walking in, especially after my last mechanic disaster, but this guy knew his stuff. The whole process took about 6 hours. Had to leave my baby there for the day, which made me a bit anxious, but it was worth it. The final bill came to a bit more than yours because of the extra cleaning work, but honestly, I'm just glad it's fixed. Just drove home, and the heating is working perfectly, nice and even warmth throughout. Those error codes have disappeared too. Such a relief! Really appreciate you sharing your experience, it gave me the push I needed to get it sorted before winter hits. Thanks again!