What year ford ? I have a 92 F150 in the back of the truck there should a connector usaully on the drivers if you unplug it, you will have either 7 or 9 pin plug. With a test light and a freind Test each pin (should be female) Have your bud put on lights. Move the test light to each pin, when it lights up tell him to turn off then back on that's so you know it not a constant power source. Do the same thing for the turn signals, Reverse lights and then brake lights.
If they all work then the short is after the connector, then I would pull the tail lights off and ***** each wire to the bulb connector with your test light same concept as the connector. When I lost my brakes lights I had power to everything at the connector so I changed the wiring harness to the lights themselfs ( I had a spare one). If you have power to everything at the bulb connectors then it might be the bulbs or to much grease in the bulb connectors. Good Luck
Last edited by Fordmon; 09-09-2009 at 11:48 AM.