I have a 99 f150. Lately when I shut the truck off and take out the key it acts as if the key is still in the on position. The lights on the dash kick on and the radio turns on. None of it stays on however. It kicks on and off and eventually drains the battery. I'm not much of a mechanic so I'm not sure where to start looking. Is it the ignition switch?

 

The key cylinder operates a rod that goes down the steering column to a switch
The switch closes power to various main circuits.
Something going on with that movement function.
Good luck.

 

Make sure the lock cylinder is all the way back to the off position, lots of older vehicles the key tumbler portion will wear out and allow the key to be removed prematurely