Hey Roost, Welcome to the site!
My 90 G30 also has an inop CC. The Brake fuse must be good, and there is a brake module on the Driver's side above the battery. Mine is faulty, and throwing a code. The FSM has a dizzying diagnostic array of what may be the cause.
The switch is a weak link, but you got that so....
Hope you have luck finding the fault. Good Wrenching!
"Who New? Blue"
1990 Chevy G30 454
Church Van, maternity division
1988 Dodge B250
'94 Dodge B350 www.xplorermotorhome.com/
Xplorer MH model 230 230 hp MPI 360 LA Wedgy OD auto
Old vans never really die if we chose to let them live