That happened to me once. The bricksters helped me out. If it does that, that means one bulb on one side of your car is pulling a little more power than the other on. That's how the light is actuated. By one bulb pulling and the other not, or not as much. They said that when you get the bulbs in one package. Use both bulbs. Switch out both sides. Since the bulbs were made closely to the same time they should pretty much pull the same power. Be Safe