Hey everybody, new here, thanks for being here! I have a 1989 740GL with close to 400,000 miles, still runs pretty well. I started having to smack the dash a couple years ago to get the fuel and temperature gauges to activate, and that went fine for awhile until one day when I smacked the dash, the speedometer needle dropped to 0 and hasn't worked since. I've removed the instrument cluster since, to see if there's anything obvious (duh- of course there isn't) and now have several issues; neither the dash light, fuel gauge, speedometer or odometer work. The clock, tachometer and temperature gauge all work fine. I'm wondering if there could be a common cause to this. I will say I believe I got the center connector behind the instrument panel plugged back in, but I'm not 100% certain. Fuses look good, so it's not that. I'm having some trouble locating an accurate troubleshooting guide for this sort of thing, and trying to avoid a trip to the $95/hr. mechanic fees if at all possible. Any info will be immensely appreciated.

 

I'd start with the circuit board. Refloat the solder points which are probably cracked, with a soldering iron or get another board. Make sure the plug is back in, naturally!