So even w/ the key in the on position, engine off, the warning lights are dim? Did this just happen or has it always been this way? You may have to pull the cluster and check voltage to anyone of the dim lights, then check grounds. Really weird problem, really sounds like a bad ground... Ever see a car with 1 dim headlight? Bad ground.
Wish I knew were your cluster ground is located, there's so freakin many! My electrical trouble shooting book goes back as far as 86. Anyone else?