Most old Audis have the CC working intermittenly, our 98 A8 also has the problem, we haven’t had time to check into it since we don’t use it so often. We accumulated all the links to websites that we stumbled into for our references.
- Vacuum diagram
- Resoldering caps on controller
- Resoldering caps on controller2
- Resoldering caps on the controller3
- CC Diagnostic.
- Vacuum Unit.
- The best write up for fixing