Help please from g29 owners

[ori]

As some of you know, I’ve had an issue with the rear demister not working properly on my car.

Long story short, BMW have this going on with multiple cars. They have identified the cause, but have no idea how to fix. BMW technical have a car that has the same issue so they gave me my car back (this was in May).

Since then….radio silence. Nothing. Today I walked into the dealership and demanded an update. The update I got was BMW technical still haven’t come back with a solution. Obviously I’m escalated the situation, but this is where I need the forums help.

Can you go into your car, turn on the rear de-mist. You will hear the relay click on.
Now turn the steering wheel slowly all the way to the left and then all the way to the right.
Let me know if you hear the relay click off while you are doing that. On some cars it’s full lock before it happens, on others it’s a slight turn of the wheel.
When the relay clicks off, the light on the button stays on. If however if you press it, the relay will click on and off again.

Please let me know if yours does it or not.

Thanks in advancen

 

[larryjune508]

That correlation with steering angle is actually a really useful clue, even without testing it myself. A fault that only shows up at certain wheel positions usually points to something in the wiring route near the steering column or clockspring, not the demister circuit itself being faulty.

Something in that harness path is likely getting pinched or losing contact at specific rotation points rather than it being a relay or demister element problem.

Worth mentioning to BMW techs specifically if you haven't already, since "fault correlates with steering angle" narrows the search area a lot more than just "rear demister doesn't work sometimes." If they're treating it as a demister fault in isolation rather than a wiring route issue near the column, that might be why they're stuck on a fix months later.

 

[ori]

Your logic is correct. The thing is they have identified that it is a power issue not a steering sngle issue. For some reason when the power steering t draws current it trips the power management to low power mode and switches of the de mist.
They are aware of it.