I have a 96 f150 with a 302 automatic tranny. My starter died a year ago and i replaced it and the starter solenoid truck Ran good for 11 months. Starter died again and i replaced the starter and solenoid. Drove for a week. Everything was running fine.
Now the starter is running without even havin the keys in it.I then put another more expesive solenoid on.Same prob. So i crank it and disconnect the S wire (which is the supply from the ignition switch i believe) and turn the egine off remove key and bam the starter is still running again without the key or the ignition connected at all?
Any advice would be greatly appreciated. Im at my wits end.

 

Apparently the problem is in the solenoid that is mounted on top of the starter. UNLESS there is something connecting the large and the small electrical terminals on the solenoid mounted on top of the starter. This is not likely but I thought I would mention it as a possibility.

I think you will have to replace the starter again, complete with the solenoid mounted on top of it. Your fender mounted solenoid(relay) should be fine as is.

 

Use a test light to see if power is getting through the solenoid on the fender with the key off. If so that solenoid is no good.
Otherwise it's at the starter.
Both should be under warranty.

 

That's a good point and a WHOOPS on my part.

I don't generally think of the fender mounted solenoid sticking internally on a 1992 or newer truck where the main power source for the starter runs direct from the battery to the starter and NOT THROUGH the fender mounted solenoid. But it can happen.

All that goes through the fender mounted solenoid is the signal to activate the starter on a 1992 or newer truck. But the solenoid can still stick internally.

 

The insulation was damaged near starter causing both wires to short out. Fixed it

 

That's the good thing about electrical problems - they can be a pain to track down, but once you do they're usually a very inexpensive fix.