RepairPal Certified shops can diagnose and repair your 1993 Audi 90 Quattro. They provide transparent pricing with a minimum 12-month or 12,000-mile warranty on repairs and services.
I think you need to check the fuses first, then if that's no good, find an Audi specialist or an auto electric shop.
If you want to find a specialist, here's a directory link for you:
https://repairpal.com/audi-repair-in-cary-north-carolina