No Limate controls or radio

I have a 1990 vette, 350 automatic, last week, the radio sent out, the power was still their, but the buttons didn't light up. Then, the next day, the climate control stopped working. When you hit a pot whole, everything works, for 20 minutes, then I get my 3 --- on the climate control and no buttons are lit up, the same with the radio. I check all the wiring harnesses under the radio, steering column and glove box, can't seem to locate my problem.

i did find a ground screw on the firewall under my steering column, but I couldn't find a wire anywhere near it. I'm stumped. Anybody have any thoughts?
Thanks.
rich