I'm wrapping up work on a rather huge project: taking the guts out of a wrecked '88 GTA, and putting them in my gutless '90 Firebird. I've swapped power trains, suspensions, wiring and dashes between the cars. I've almost got all the bugs worked out, and if I can find a diff for the stupid ozzie 9 bolt unicorn I have under the gas tank, I'll have a working car, but I've run into a problem that's vexxing me.

The digital speedometer is alternating between showing a reading of 100 with nothing else on the gauge lit, and the whole gauge lighting up (meaning all the segments are lit, like an ops check). I've been looking for a short, or a disconnected wire, but I can't seem to isolate it. What's worse is that it is intermittent, so I'll jiggle wires and harnesses but it keeps coming back just when I think it's gone for good . Does anyone have experience working on these digital units that has an idea of where this is coming from?

 

I just took out my cluster to clean it. When I put it back in my speedometer does nothing but display 100. Then I drove around and it blinked with the speed signal and digits cut in and out and so did the KM/H and MPH stuff. Then when I parked it every element on the LCD was lit. There are no wires to cross. Help! I keep getting this thing farther away from being able to pass inspection.