I recently bought this truck, and this is starting to drive me crazy. When I leave the key in the ignition, and open the door, I get no warning sound, but if I take the key out and open the door, I get the "key in ignition" warning sound. Something is obviously backwards on wiring somewhere. I looked under the dash and saw that someone previously had an alarm or remote start at one point, I can see the plugin harness and some relays... I'm pretty sure that's where the problem may be. Any ideas on how to get this functioning correctly?
Thanks.

 

How old is the truck? Most dealers have all the cars on the lot equiped with alarms, to protect 'em while they're on the lot and PRIMARILY to hope to sell you a high profit alarm system that's already installed. The last several new cars and trucks I've bought have had this installed when I bought them. I always tell them I don't want it and they simply send the lot kid out to pull the "brain" out and it's done. They leave everything else in. I just leave it all in place because it doesn't hurt anything. There are generally 2 relays in the system and they are in "rest" mode so no need to do anything with 'em. Sounds lik,e they COULD have something hooked up in a way that caused the problem, but I am betting it's something else. The "key-in-the -ignition" contacts used to be at the end of the key when it's inserted. I don't know it it's still there or not. There should be 2 very small wires going to the switch wherever it is because the switch simply completes (or breaks) a circuit when the key is in.

 

Can you post some info on your truck or complete your profile ?

Dad's '01 had an issue where the tab in the end of the key cylinder broke off, but his symptoms was key in ign warning when the door was open, regardless if it was or not.

Could be the key is holding it up, where when you pull it out, it falls into place to signal the warning device.

This thread, LMC explains how to pull the key cylinder out to check it.

https://www.f150online.com/forums/el...beep-beep.html

Did this on dad's '01 and when I pulled the cylinder out, the tab fell out on the floor. Took a look and the cylinder was clear, reinstalled it and no more warning tone ( with or without the key ).

 

I took it in to have the remains of the alarm removed, that seemed to fix the problem. I think the wires that trigger the dome light might have been reversed or something.