[Three_Fingers]

Try giving the dash a goodly smack. I'm serious! I have a problem with the dash illumination and oil pressure gauge on my '87 Caravan and this makes it work right again.
Most instrument clusters have plug-in ribbon cables connecting the cluster to the various power supplies and whatnot and the vibrations sometimes make these connections come loose-that and dust/crud buildup on those connector contacts can make the problem worse.
Aside from opening up the dash and removing/cleaning/reinstalling the connections-just hit the sucker.