Something is keeping electrical power from getting to the brake lights or from the lights back to the negative terminal on the battery. In other words, there is an "open" condition in the circuit.
There could be many causes:
I'm sure that there could be other causes, but these are all that come to mind at the moment.
Above the brake pedal. If your main brake lights dont work but your third center brake light does, then the brake light switch is not the problem. Its is the turn signal switch.
Check the brake light fuse. If you have 12 volts at the brake light switch I would suspect the signal light switch is at fault.
Check the fuse, the bulbs, and the brake light switch.
Check the brake light fuse first. Then check for a bad brake light switch at the brake pedal.
I dont know because i dont have a FORD Check your brake light switch on the back of your brake pedal for adjustment.
check your bulbs
look at the top of the brake pedal under dashboard you can usually adjust them so the brake lights dont stay on.
Check for power at brake light switch Check for power and ground at the brake light sockets open wire?
The fuse may have blown. Be sure the bulbs are good.
Check the fuse, check the bulbs, check the brake light switch, in that order.
Check the: Bulbs Fuse Stop light switch
it could be that your brake light switch under your dash that sits right on top of your brake pedal has gone out