I am having an interesting issue in my 91 740 turbo: every so often it seems that every so often the speedo, tach, cooltant temp, and fuel gauges go inop. By that I mean they behave likenone of them are getting power. But later on the same day they come back to life. It may be coicidence but it feels like that usually happens first thing in the morning; at first I would guess humidity but AFAIK the power wire to those gages in the cluster come straight from the fusebox. Where else should I be checking?

If this matters we may have a clogged ac drain (clogged enough to drip inside while also drippri g though the drain).

I would check the simple stuff first. Has anyone had the instrument cluster out? Are the connections fully seated? Wrangling around with that cluster, it is easy to occur.

Check the FAQ -- sometimes gauge weirdness can be the ignition switch if accompanied by accessories not working (radio, etc.)

Sounds like you may need to reflow the solder on the back of the cluster. If speedo problems persist, it's time to dig into there and check the status of the capacitors. Lots of good info in the FAQ.

Clean that A/C drain ASAP to keep the floors from rusting out... you can get at it from underneath at the base of the firewall.

-Ryan
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Athens, Ohio
1987 245 DL 324k, Dog-mobile, E-codes
1990 245 DL 137k M47, E-codes, GT Sway Bars, GT Braces, Dracos
1991 745 GL 304k, Regina, 23/21mm Turbo Sway Bars

I think you meant http://www.brickboard.com/FAQ/700-900/ElectricalInstruments.htm#GaugesStopWorkingIntermittently, right? I will pull the cluster out this evening when I get home and then do the resoldering stuff.

What I was able to do this morning was check that I was getting voltage to pin D4, which seems to power all gauges. I also found out the temp gauge was working (or decided to); I will keep an eye on it.

I did clean the grounds behind the ECU; I can check them again.

When you mean from underneath, do you mean on the engine side or in the cabin?

Drain is accessible from both the engine compartment (on passenger side firewall) and from the cabin if you remove the glovebox. I'm addressing a rotten grommet in mine.