doing my electric fan today. is there a good source for switched power near the battery-fuse box location?

 

I ran mine constant off the battery and ran a switch in for manual use, that way the fan will cycle if the temp sensor sees it as too warm regardless of ignition switch position.
I originally ran the switch in case I miss-judged the setting on the temp sensor and needed to turn it on manually, but I've got the setting right and never use the switch.