How do you check the resistance of the ground under load?

Its a 93. I have been using the diagrams here: http://forums.audiworld.com/s4s6/msgs/243113.phtml + Alldata. If you have something better I would greatly appreciate it.

Unless it first wants to see input from one of the devices it controls I don't understand why it wont power on at least. I can't imagine the AC head wanting so much current that a weak + or - lead would keep it from working.