Why do you want it on the power. If its for the servicething use a switch on the ACC, not the power line. That's what i'm doin. This uses little current. Using a switch on the power line is only if you want to completely cut power off the PC, which is not your case. you only want it not to turn on during service.
Edit: sorry JimmyFitz didn't see your post, but anyways, What JimmyFitz said.