Yeah, so there is 12v on the violet wire whenever the fan switch is sending the demand signal to the PCM. I wouldn't use that for a constant-on 12v. Do you have the power point next to your radio? Power point or cig. lighter are probably your best bet for constant-on 12v.
For my purposes, having 12v on that wire solves all my problems! Of course, I got the LED to light up, but I think I wired the switch wrong- the LED comes on, but not the AC! Moving the output wire from "ground" to "load" terminal, and bringing in an actual ground wire should do the trick. It appears that the ground on the switch is just for the LED, and is isolated from the "signal" portion of the switch.
The LED is so frickin' bright I'm going to have to either color it with a sharpie or put a resistor on the ground wire to dim it down. I wanted an indicator- what I got is a blue map light!