I have 1992 F150 XL 302 E4OD 4x4, manual locks and doors.
I would like to add a hidden kill switch for added security. It would make me feel better if there was a more reliable system in place to keep the truck from being stolen. I have heard of other truck thefts and would hate to have it happen to this truck as it has been good to me (knock on wood). I use the door locks and a steering wheel club now but those are easily defeated.

I was thinking of putting the red/ yellow wire off the load side of the fuel cutoff inertia on a new(hidden) switch. I was expecting to see (2) wires at the inertia switch, power in and power out, separated by the inertia switch.
I see 3 wires going to the inertia switch? What could the 3rd be for?

I consulted the Haynes manual for wiring diagram(see photo) and it looks like the green/yellow wire is the 12v feed in and the red/yellow is the switched power out the the fuel pumps.
The diagram shows a 3rd contact at the inertia switch but does not show it going anywhere nor does it list the black/ orange wire.

I assume I can just ignore the mystery black/orange wire and cut into the red/yellow wire as planned to add a hidden kill switch but I thought I'd see here if anyone knew the purpose of the black/orange wire?


Anyone else done their own kill switch and have a better plan? Ignition system maybe? put a switch on the power to the ignition coil?

 

Don't take this the wrong way, but no one wants to steal that truck. It wasn't a popular target when it was new, and it's not getting more-popular 27 years later.Not only did Ford never actually wire it to anything; they wired it wrong for what it was designed for. It was supposed to be for an indicator light in the instrument cluster, but they goofed the wiring harness, and abandoned that socket in the cluster. In '94, the cluster was redesigned to eliminate (or repurpose) that socket. You can easily fix the wiring goof, and add a bulb if you like:


(phone app link)This site is usually more-complete:
http://www.bbbind.com/tsb-wiring-diagrams-database/ANYTHING you find or post on the interwebz is likely to be found by a car thief just as quickly as he finds your truck. Google works for thieves, too; and it works while you're sleeping. So don't expect anything you do to even slow a thief down. If he wants your stuff, he's going to get it. Pay your insurance premiums, and make sure you're covered for REPLACEMENT VALUE - not actual value. This caption explains a few options that might momentarily confuse a joyrider or vandal, but they won't work on a professional car thief:


(phone app link)

But like I said at first - no thief is out looking for '92 F150 XLs.

 

You're probably right and I should just scrap the idea.
Glad to know what that mystery wire does!Thanks again for answering my questions Steve