Odometer/gear selection indicator not lighting up

I have a 99 Silverado and the Odometer and gear selection indicator does not always light up. (it works sometimes.)

The odometer is still registering the miles....even when it's not visible.

Any ideas?

Help.........

I had the same problem with my 99. The problem seemed the be the re-set switch on the pc board. The display you see gets its power through the re-set switch. I took the entire guage cluster out of the truck and tapped the side of the re-set switch with a screwdriver. The switch is about a quarter inch in diameter. The plunger that you push goes down and hits the switch. After tapping the switch, it illuminated. I took the cluster in the shop and hit the two points where the re-set switch is soldered to the pc board. It has been working fine ever since.