Taillight gremlins

[jpfletch1]

A friend recently told me that my brake lights were not working. So I started with the obvious and changed the bulbs. No effect. So I took the taillights out and started trying to figure out why the lights would not go on. There are two wires coming into each taillight. One is for the headlights and the other is for brake lights and turn signal. When I test each wire each one of them has power. When I attach the headlight wire to the lamp socket the light goes on. When I attach the brake wire to the socket the brake light will not go on. Thinking maybe it was a bulb problem I attached the headlight wire to the opposite clip and the brake light went on. Therefore the bulb is not the problem. Then I thought maybe I had a ground problem. So I attached a wire to the frame and into the taillight assembly. Same thing the taillight will go on but not the brake light. When I take the bulb out of the assembly and looked down into the socket I put my voltmeter to the small bump where the bulb connects and it has power. The puzzling thing to me is why when I put the bulb back in no power goes to the brake light filament. The bulb is orientated correctly with the short and long side in the correct grooves. Does anybody have any ideas on what to try next. Thanks