[Al Skierkiewicz]

Two things to look for...
First, always check that the hardware inside the light is tight because any wires that are under hardware conduct power to the light and motor. Since the light is intended for use on automobiles the body of the light is one side of the power supply. The mounting hardware is designed to conduct and needs to be tight to make that happen. (The lamp "on" is only relative...how bright is bright?)
Second, check the connections on the Spike. If you haven't measured the current to the light you will be surprised that it is a lot higher than you think.
Al