that ground [to the dome light] is what turns the dome light on, the switch itself is grounded by the case held against the dash by the ferrule nut, so the dome only gets a ground when the knob is turned to that position
"When we tug a single thing in nature, we find it attached to the rest of the world" ~ John Muir "When we tug a single thing on an old truck, we find it falls off" ~ me Some TF series details & TF heater pics