[km23honda]

I don't know its just a thought. But you may have hooked up the power wire to the light of the lighter. So when you trun on you headlights the wires cross and trun on thing off. I don't know if that makes sense. You could try a swicth that is what i have to my car. Direct power a good ground and you are done easy a cake.
A ground wire is as good as you make it. Really all you have to do is place the ground wire to a bolt or screw on the car and its grounded.