Yer right. That thar wire goes to the brake warning light. It is not a sentry to tell anyone that the engine is running. It just is. Oil switch is a freestanding separate circuit that uses a grounding switch (the "sender" to complete the bulb circuit.drober23 wrote:Colin,
I have a Bentley, and have been using it to diagnose the wiring. blue goes to alt light, and brake switch.
I believe it serves the same purpose in these two points, as well as at the oil switch and fresh air fan switch in the engine compartment. It tells whatever it is connected to that the engine is running.
In my case, there was power feeding back into the blue wire from the brake warning switch.
Once I sort that out, I STILL will have to deal with the overcharging problem.
That regulator D+, that sends 12 volts to the alt warning light to shut it off, also gives the heater blower relay coil the voltage it needs to hold the heater blower relay contacts closed. Your heater lever grounds that relay circuit to energize the heater blower motor right off the starter hot terminal.
Experiment. Disconnect #61 blue from the brake warning light. Protect it from shorts. See if that drops your charging voltage.
Colin