Originally Posted by BikerBob
Yes I have tried the dimmer and nothing, the steering wheel control lights are also out. This happened last week in heavy rain.
Pardon a dumb question, but have you checked to make sure your exterior lights (i.e. taillights, etc.; all _except_ the headlamps) are still working? Not sure about the Bonneville, but on other GM cars I've owned, the dash backlighting is a separately-fused branch off the exterior lighting circuit, so that if you manage to blow your outside lights, your dashboard will go dark as well, to alert you that you've got a problem.
Your headlamps are not involved; those are on separate circuits protected by circuit breakers. But all the other external lights (those on brown wires) are on the same primary circuit as the dash backlighting.