PontiaCat59.....I would doubt that you have a short, as that would cause a circuit breaker to trip, or a fuse to blow, or in extreem cases burn up the wire. What you seem to have is an intermittent open circuit, and/or a poor ground. I would tend to think the former. The bulb has two filiments in it. One is for the running light, and the other is both the signal light and the brake light. The power to the brake lamp goes through the turn signal switch so that the filament can blink when you activate the switch, with the brakes applied. Check the connector and pins on the turn signal switch located on the lower part of the steering column below the dash......John