For the past 6 months I've had this issue with my dash lights 'flickering'.
When I'm driving to work in the dark early hours I have my headlights on. After about 10-15 minutes, the dash lights that illuminate the cluster dim to about 75% of their regular brightness and the blue highbeam indicator light comes on about 1/2 of it regular brightness along with both turnsignal lights, both staying on solid also at 1/2 of their normal brightness. If I smack the top of the dash over the cluster it will correct itself for a few minutes to seconds and the repeat the problem. If I hit a bump in the road or go over some railroad tracks it will bring it on or correct it if it's flickering. If I flex the steering wheel up a little it will correct or reproduce the issue. When I do that sometimes, the tach will drop 50% of its RPM of what ever it is running at at the time. I have tried the wiggle wire test behind the cluster with no results. I seems to only happen after the cluster has warmed up. When I drive with the lights out and turn the lights on at dusk, the problem begins immediately. My question is, are there any solder points on the cluster's circuit board that could be breaking down to be re-soldered like a fuel pump relay needs on occassion? Sorry for the long but frustrating post. I really hope someone out there can direct me where to look next.

Thanks.
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'86 sedan with 471,000 miles on the original engine and automatic transmission