Service Lights Flickering

[Kenneth1948]

My service lights on the instrument panel flicker while driving. Also speedometer only works intermittently. I'm not sure if these two symptoms are part of the same problem or not related. This does not seem to affect drivability.
It seems likely it's a bad ground somewhere, possibly in the instrument panel. Any suggestions where to start looking?
All help is much appreciated, John Kenneth

[DesktopDave]

I'm thinking you've got some loose wires, it's a pretty common problem. The speedo could be the result of a loose connector too, later models generate a electrical signal from the differential rear cover. That connector is prone to water contamination.

There's a few odd single wires plugged into the E24 gauge cluster too, don't recall what they're for (cruise control signal? OBC?). Regardless, all those old-fashioned board-edge connectors are prone to working loose over time. The complete service light assembly is a pretty loose fit, from the clusters I've seen.

I've resolved other gauge problems like that in my E30s...it's a very similar setup. If you feel like pulling the cluster, there are two small nuts that provide grounding for the gauge motors. Sometimes they work themselves loose or corrode a bit.