Fuel and Temperature gauges shut off when not moving

[Jon]

I have a '93 850 GLT with a 5-speedand 171k miles. The car seems to run fine, but when not moving the temperature and fuel gauges drop to zero. As soon as the car moves (and I mean less than a crawling pace), the gauges come back on and work normally.

The most annoying part in all this is that it also seems to effect the service interval light which recently came on. I went to clear it and nothing happens. The little light on the diag connector just comes on and stays lit. I tried checking for blown fuses and for lose wires on the back of the gauge cluster and found none.

Just to add to the problem, in the process of removng and reinstalling the gauge cluster I set off an SRS code, but that light is totally uneffected by the problem. The tach and maybe the speedometer (there's not really any way to tell with that) seem to always work fine, as do all of the other warning/indicater lights.

I'd really prefer not to have to replace the gauge cluster but if it must be done it must be done.

[Jon]

I suppose this is a really wierd problem. I'm sure it's just a lose ground somewhere. Damnit, I need a wiring diagram.