If something is not polarized such as the outlet or the plugin, this could cause a problem. The quikest way to find out is to interupt the ground plug. If the ballast come on without the ground, it's wired wrong. If this is the case, don't touch the hid box because you'll get a shock. The wires coming from the transformer are usually marked, (common) to white, (120 or 110ac) is the black wire, and the ground wire the green one or a wire without insolation. Trace the common wire back to the outlet and it should trace back to the wider receptacle slot in the wall socket. Do not come in contact with the leads coming from the tin can thingy. The capacitor can stay energized even after the electricity is disconnected and you will get zapped. If the plugin wires are hooked to the transformer backwards it will produce a short when using a grounded receptacle. If the wiring is ok, You'll need to replace the transformer. The common can also be refered to as the neutral wire also.