I think this circuit is the same on a series I and II as well?
My brake warning light was burned out so I replaced it. It was off and working fine with the brake reservoir float level switches. When I operated the hand brake the light would not come on so I got into where the switch was and tested the switch. The brake switch is working fine but I have no voltage at the black and white wire that feeds it. Also the brake light is always on despite removing the wires from the reservoirs. So in playing around by the switch I must have grounded the circuit?? I can run a new wire to the switch but I can’t get the light to go out. I have a wiring diagram but it doesn’t tell me where the black and white wire actually connects in the dash. Any hints, clues?