Trying to isolate where the issue is that is preventing my driver's door contact switch from receiving power. Headliner has been removed. All other functions work- illuminated mirrors, dome light, passenger side contact switch. New switches at both doors. The plugs are clean. Grounding behind the instrument cluster? Where is the source of power for the driver's contact switch?

It's located at the end of the battery cables.

That's probably not the level of detail you were looking for. But, without knowing the year/model, it's the best I can do.