There is no ground wire. The alternator is grounded just by it being mounted in place.
So where is the ground wire at?
The alternator is grounded by the outside casing mounted to the metal mounts when the alternator bolts are tighten up. It is grounded to the engine itself threw the mounting brackets.
Check the connections under the rear seat cushion, that is where most of the major connections are located, Caddies are kinda different with thier wiring setups, if you believe your having grounding issues you can always add more grounds, but I have found most issues under the seat.
Looking for a Used DeVille in your area?
CarGurus has 22 nationwide DeVille listings and the tools to find you a great deal.
Search Cadillac DeVille Questions
Cadillac DeVille Experts