I am working on a Ford F 150 4X4 351 . The truck starts good but will not turnoff when key is turned off. I have replaced ignition switch did not help. Checked wiring for breaks none found. The coil has power and sparks when ignition switch is off. I also noticed when turning off switch the interior lights brighten up, engine runs on. This is not dieseling.
Any one have some hints ?

 

Well, I'd guess that the wire to the coil is shorted somehow to B+. Its entirely possible that the ignition switch itself is at fault?

I must assume if it is an F-150 (and a 351) it isn't a 67-72? Does it have electronic ignition?

Did this problem just start after some other work?

 

1985 truck has electronic ignition. havent checked coil for short.
Bought the truck in this condition.
Ignition Switch is new, did that first.