Cruise control on 2003 f150 fails to engage intermintenly.

 

Replace the master cylinder pressure switch with a Ford part, not an after market part.
Sounds like the switch is going open contact from fluid expansion after the engine bay heats up.
Good luck.

 

This is the switch:


This is also a repost, there's another thread with a reply:

https://www.f150online.com/forums/el...ough-road.html

 

Yes it could be a brake circuit issue as well.
The pressure switch has normally closed contacts to provide 12 volts to the CC module.
When brake is applied it opens the circuit shutting down the CC.....AT THE SAME TIME
the brake circuit 'applies' 12 volts as an 'inhibit signal' to the same Module.
This is a dual kick off action required by law so the CC doesn't force you into a preventable accident.
Good luck.