I wired both the power and ground wires for the switch into the accessory cigar lighter.
The fan switch till has power all the time and can be turned on anytime regardless of the power shut off.
It'* a little confusing because the radar detector only gets power when the key is on and when the key is turned off power only stays on for the 10 minutes accessory delay off feature.
I wired a light in line with the switch so it tells me when it'* on so I don't forget and drain the battery. Thanks for that idea PontiacDad.