Tim,
You probably already know this, but your second choice and the third choice are basically the same...just a different location in the same circuit.
Anything that is switched is done so with the only switch available, the ignition switch. If your heater is wired to turn off as you kill the engine and leave the truck, it is accomplished with the ignition switch.
What I'm saying is that the powered side of your fan motor is only the other end of the wire from your ignition switch. I thought the ignition switches had two terminals, both powered when the switch was ON. This allowed the contacts to share the load and allowed for more 'leg room' to attach wires.
I will be interested in your findings on the ARM terminal of the regulator...in my pea brain, it sounds like it should work!
If your truck burns to the ground, blame Joker!
Stuart
