'95 740i - Instrument Panel Issues (not pixels)

I have a '95 740i that every once in a while all the needles will go crazy (ie speedo may jump to 120, tach may jump to 5K, then the needles all fall to zero, etc.). Then all of the sudden they will return to normal and function correctly.

When the gauges are going crazy, the BC button on the MID is not functional but when the gauges return to normal then the BC button functions normal as well.

Any ideas? Don't want to send the dash in to be rebuilt if that's not the problem.

Thanks for any help!

Chad

I don't think it is the cluster that is the problem. If it was, the BC button (which I think stands for "On-Board Computer") should still work.

The first thing I would do is check the charging system (battery, alternator) to make sure that it is putting out enough voltage. If the ECU doesn't get a steady 12 volts, crazy electrical issues can pop up.

I'll check that and see what I come up with. Would the lower voltage also cause the clock to lose time occassionally? I've noticed that the clock loses time but it seems to be sporadic and I'm wondering if it loses time constantly or only when the gauges wig out.

I would think that it could cause issues with any electrical system that the ECU controls. So far, I've heard of transmissions shifting problematically, headlights and tail-lights cutting on and off, interior lights dimming, random switches not working, and the motor running too rich or too lean, all from bad charging systems causing low voltage at the ECU. I had a Cadillac Fleetwood Brougham that had a bad connection on the alternator causing the headers to glow red hot because the motor was dumping raw gas into the combustion chamber while the electrical systems were going crazy.

This may not be the problem with your car, but it would be the first thing I would check for.