TAZ - are you talking about a JEEP A/C or a BUILDING'S A/C?
This forum is concerning JEEPS, not buildings! I'm sure you can find a forum dedicated to house wiring - and tell them about how to wire a Jeep!
On a Jeep AC system black is ground - the compressor clutch and the blower motor uses black as the ground - sometimes called the return, sometimes called chassis ground, or in the UK sometimes called earth.
But wire your own Jeep with conduit, J-boxes, wire nuts, solid wire, you can even put a house window air conditioner in it if you want - it's your Jeep! (If you actually have one.)
But be sure to get a permit from the building department and get it inspected before you try to turn on the power.