G'day guys, here's the situation...
I bought a 1993 540i 18 months ago as a gift for myself when I started in a new job. It has been, and still is, a great car, very fun to drive with ample power and good performance. Sure beats the crap out of the old Holden Commodore I used to drive...
However, it does have some niggling faults that I am eager to sort out. Most are pretty straightforward such as soft bonnet struts and a ball joint and tie end rod with play. These sorts of things I can deal with and don't mind paying for.
The one fault that is leaving me and the mechanics confused appears to be electrical in nature, and it's proving tricky to pin down to any single cause.
Turning the headlights on triggers a barrage of error messages indicating that the headlights, brake lights and number plate light are not working. This error appears false as all were definitely working on checking. This problem has since resolved itself since the car was put in for its regular service earlier this week during which the cluster was removed and tested as okay at that point in time. The specialist seemed to think the problem was either in the instrument cluster or the light control module however did not have a spare unit to swap in to confirm this.
Another intermittent fault is that the OBC will begin displaying gibberish and will appear to scroll. This problem appears to be temperature related, in that if the car is parked in the hot sun, the problem will occur on starting. However, if the temperature is low the problem tends not to occur at all, or will only occur once the car has been running for around 30 minutes and has thoroughly warmed up. My first thought here is that this is a bad connection, possibly on the board itself and that heat expansion is causing an open connection. I've read here
that there are a number of capacitors that tend to go bad, and can simply be desoldered and replaced to fix a similar problem. Has anyone else had this sort of problem, and is there a fix?
Now, after I picked the car up from the mechanics, I noticed that the airbag light stays on for approximately two minutes after starting the car. It then goes off. Previously, the airbag light would only come on for a few seconds when the car was started and then go off immediately. Can anyone say whether this now means that the airbag is no longer working, or is this likely just to be a glitch?
Once I got the car home from the mechanics, it was dusk and the headlights were switched on. When I did that, I noticed the fuel gauge was no longer illuminated. Okay, first thought - one of the 3 x 3W bulbs that are in the cluster has gone. I took the car back to the BMW specialist and they looked the cluster over, confirmed that the bulb was actually working... but somehow the fuel gauge was no longer illuminated by it. As far as I can tell, this makes no sense whatsoever, as there is nothing to stop the display from lighting up. Is there some optic fibre/light piping that may have shattered in there that could cause this bizzare fault?
Cheers for any help that you guys and gals can provide... these glitches are merely niggling problems, but I'd really prefer not to have to put up with them!