I read the tech fact on this. If I understand correctly, the ignition must be off when adjusting. So it goes something like this: key on, measure; key off, adjust; key on, measure; key off, adjust; repeat. Can you not disassemble the APPS to the point of being ready to adjust it then turn the key on so you can watch the voltage as adjusted?

 

You have to have the key on to adjust the voltage. With no power to the apps, it throws no voltage to the wire that you're probing, and that means no signal on the voltage meter.