Most common cause, when all the brake lights are not working, is the brake light switch itself. Ford used a really odd design that was no more reliable or unreliable than any others. The next most common cause is the turn signal switch. That switch disconnects the brake light on the side you're signaling from the brake light switch and connects it to the signal circuit when you move the lever.
If the dead brake lights are accompanied by a second dead circuit in the same area, in this case the tail lights or the backup lights, a cut or corroded wiring harness would be a good suspect, especially if someone used some type of quick connector to install a trailer towing wiring connector. Those let moisture in leading to corroded wires.
Monday, October 21st, 2013 AT 8:40 PM