I have stock '86 F150 with 184K miles, 5.0L engine, and auto trans. About two years ago, I had both fuel tanks and the fuel selector valve replaced. The fuel selector valve has worked since the replacement with no issues. Yesterday I was checking the fuse panel in trying to find why the cruise control would not work. The owner's manual showed a fuse for the valve selector switch but the corresponding slot in the fuse panel is empty. As stated above, the valve selector switch works so should I put a fuse in the empty slot in the fuse panel or leave well enough alone? Secondly, I was able to locate a fuse for the cruise control and that fuse appeared to be good. What is the next step in troubleshooting the cruise control not working problem? Thank you.

 

I would stick a spare 15A in there, just to have a spare, that's #7 slot. You may have slot 10 & 13 empty as well, that's 2 more spares, like a 25 & 30A.

 

Speed Control, look this over if you don't have..

http://www.garysgaragemahal.com/speed-control1.html