After 16 months of use without any problems I have recently had intermittent problems with my electric windows. First the passenger side started to be temperamental, and occasionally the window would not lower (or raise) but after a few attempts with the lever it eventually did. One day it just stayed down and that was that. So off with the door cards and after playing around with the switch and the DNA mechanism, I thought that I had adjusted the hard stops incorrectly, so I re-adjusted them to make sure that the BMW switch was actually being pushed all the way. Re-assembled everything and put the door card back on, and bingo! All working again.
That was about 2 months ago. The passenger side is still working fine, but now the driver side has started the same fun and games. Once again I've stripped off the door card and examined/checked the switch mechanism. It was adjusted perfectly. However, playing around with the window just using my fingers on the BMW switch (and not the mechanism) there is still an intermittent fault. Window works, then it doesn't. After a few presses, maybe 6 or 7, it works again, then after another few goes it stops working. I've checked all the wiring and it is all good. There are no issues with that. It is interesting that when it is not working, when you press the switch, there is no noise coming from the motor - like its not getting any power at all. Then when it does work, you can here a faint click just before the window raises or lowers.
I've tried a replacement (known good) switch and still the problem is there. Now wondering if the problem could be a relay (Web search has not been very fruitful, but found some references to a 'comfort relay' whatever that is) or even worse the window motor itself. I am not sure how the hell I would get the regulator and motor out now that the DNA door skins are bonded to the doors. You have to remove the glass up through the door, and to do that you need to remove the seals on the top edge, which are now covered.
I don't think it is related (but who knows with electrickery) but my ETB tachometer has also gone bananas. Around the same time as I had the window issue I fired her up one day, and the tacho went right round the dial to max. I restarted the engine hoping it would reset, but it didn't. Its very random, and when driving it now works in the opposite way to expected, in that as the revs increase, the needle goes down, and as the revs drop, it goes up. When you switch off, it just stays wherever it was. Had the battery off for 12 hours in the hope that everything would reset, but no, it's still all playing up.
I have always had an issue with this tacho, in that when it was working, it would show the correct rpm, but if you took your foot off the gas the needle would just dive back to zero, and then pick up again as you apply the juice. As it's such a ball ache to remove the dash to remove the dash to get this out, I have just put up with that little 'feature'. Now I'm wondering if it has been faulty all along and finally gone pop.
Any ideas?