Mystery wire in headlight harness

So I checked on the otherside of the bulkhead connector... same dark green/white stripe wire. I haven’t tried tracing it yet. The only reference I have found is on a Charger diagram in the FSM. Z for a 1969 Charger is dark green/white stripe I have, but it doesn’t go anywhere. See attached. I’ll see if I can trace it to something.

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