well, it dont matter which wires on the light you hook up to ground, but one has to be grounded. Make sure the place you are grounding it is actually a ground. Theres lots of metal peices in the dash that dont actually get grounded.
You only have two wires on the dimmer IIRC... if the light is grounded and the bulb is good, either one will turn on the lights when the lights are turned on. Just one wont dim. So if you dont have anything turning on, chances are its not your power source.