I have a 1993, F-150 with a 351, AT, 4 wheel drive. My problem is, when you turn the key on it "clicks" and everything goes dead. I can move the positive cable on he battery and get power back. Tuen the key same thing. I have cleaned the battery cables both ends, removed and tested the starter, checked fuses and pound my head on the fender. Could it be the starter relay on the fender?
It did have a cheap remote start on it that I have removed.

 

is the battery good?

 

Yes the battery is good too.

 

Just because the ends are clean doesn't mean the cable in between isn't corroded or messed up.

 

You've got a bad cable or connection somewhere. Take all the connections apart and double check them. I can almost guarantee it's not a component problem.

Get someone to turn the key while you watch the cables, you'll likely see or hear the problem.

Another test, hook a jumper cable from your battery negative post to a bolt on the engine and try it again. If it goes you negative cable is bad.

If your battery cables have those clamp-on replacement ends, throw the cables in the garbage and go buy new. When those ends are installed it opens the cable up to moisture and corrosion. I've cut the insulation off of cables and found them green from one end to the other.