I just bought a truck and it has a switch that interupts the ignition wire, with the switch off all the accessiories will turn on but truck wont start til switch is turned on.

I tried to eliminate this and connected the wire back together but when i did this i start the truck and the cab lights and door locks flicker on and off for about 4 seconds like the truck is haunted
My best guess is maybe this is bc of a short somewhere but i dont know, and dont know where to start lookin for one.

ANy ideas of how to fix this? besides an exorcism

 

Check your interior junction block or fuse panel under the dash for corrosion due to water intrusion, very common for this generation F-150/Expedition.