my 1973 240z has two electrical connections on one end of the wire harness and a black wire on the other that a bolt or screw would go through to ground it. when i ground this wire to the car, it stays hot all the time, and runs my battery down. what should i ground it to that that won't make it hot when the ignition is off?

I'm no electrical wiz, but I believe that if you ground it to anything, it would stay hot all the time. I think it would need to be connected to a switch or relay in order to have 2 states (grounded, or not grounded, in essance Hot, or not hot)