1992 5.0 dash lights wont work

Bought this car, dash lights worked but climate control lights didn't. Now dash lights don't work either. It has an aftermarket (?) background. Tested rhe fuses, they are good. Tested the dimmer switch, it is good. Took the dash apart bulbs are good. Question is it has a box that the dash plugs into and thinking it might be bad? We are at a loss what to do next. Also, it seems that the dimmer switch was bypassed. Please help!!