Fuse keeps blowing when I press the brake pedal on a 98 Windstar. Brake switch is good. Inserted new fuse and the brake lamps do not light up before the fuse blows. Removed all bulbs front and back and the fuse still blows. What to test next?
Shorts in this system are almost always in the rear of the vehicle. Remove all the brake bulbs, including the center light and inspect the sockets. Carefully inspect anywhere the wires move, like at the trunk lid hinge. Next look for any added trailer wiring connectors, if any disconnect them. After each part is disconnected retest. A short finder tool saves having to blow a bunch of fuses with testing. Year make and model might help...
Disconnect battery. Get a continuity tester or a multimeter. Remove bulbs from holder. Test the HOT side of each holder. The ground after all is grounded so the short must be on the hot +12v side. You may find one side or both are shorted. Check your trailer hitch sockets as @Fred Wilson suggests. Also, check your wiring scheme - does the brake switch connect from hot directly to the bulbs or does it go to a relay? The relay could be bad. Some cars - the hot goes to the switch and when the switch is closed it goes to a relay. That then powers the bulbs. So if there's a dead short in the relay, it can be blowing your fuses.