Horn does work
 

Forget you are not mechanics

2003 f150 4.6 Horn does work
 

Check the horn is good, the ground wire is good. Check the voltage at horn harness when horn is pressed 4 volts measured. checked the voltage at horn wire at the fused box 4 volt. rotated the relay in the fuse box same volts.
Any suggestions.

Not sure what you need help with. You said your horn does work.

Ha

Vstn, I merged your two threads on this problem. Duplicated threads lead to confusing responses that can waste your time. I wanted to delete the second post here, but I can't do it until the redirect expires.

To clarify, you are saying the horn will make noise if you apply 12V to it, but that it is only getting 4V, right? And, you want to know how to supply the needed 12V.

- Jack