F-150: Any Chance Of Making All Cigarette Lighters Switchable?

I don't have your manual, but if all the lighters are on a single fuse, then they are from a single source. If there are separate fuses for, say, front and rear lighters, then most likely there are separate sources.

And don't rule out the possibility that they are computer controlled outlets. Don't know about the older F-150 but my sister has a nearly new one and had a shop hook up an extra cig lighter type outlet to the existing outlet wiring. That confused the computer and kept draining the battery. Dealer couldn't figure out what was going on. I told her to tell the dealer to check on the possibility it was messing up the computer and that did turn out to be the cause.