put your meter lead on the red or white and the other lead to anything metal on the chassis of the unit (ground). It should register 120VAC. If not, as Handyguy said, someone may have mess w/your disconnect. This is simple a metal box and may have a switch, fuse or a plastic piece that you pull out to cut power to the condensor unit. Also, check inside the indoor unit and find where those red & white wires originate from and post a pic for further advice.