Hi,

Yes, that is a nice trick of using headlights to make the alternator kick in.

Part of that charging system is through the battery light in the cluster. The light circuit goes to ground via the alternator's housing and a separate grounding wire.
I would check that out and the D+ wire on the alternator that comes from the dash.
It carries "exciter current" to kick the alternator some juice in its first few spins.

Backing up to the cluster now.
You have a fuse panel and one of them feeds the cluster and the cluster has to have its own grounding wire to make all of the other functions work.

I can only speculate that somehow turning the headlight switch gives something a grounding path through its circuitry. Maybe it via the parking or turn signal lamps coming on.


It all sounds pretty wild!

Phil