ac does nothing when turned on

[oakland ironworker]

Prepping for trip and no ac. checked voltage at thermostat and its only 6.3v, marking on pcb says +7.5. I thought I was suppose to have 12v. Checked all 12v fuses and they are good. Checked 110 leaving ac breaker and its good but black wire coming in to ac unit is dead. Checked continuity with one of those radio frequency tester (Neighbor is an electrician) and white was good but black was way weak. Should that wire be hot. Read on one forum someone just ran a wire from the breaker to the ac to see if ware was broken in ceiling. Help its hot
Greg

[DQDick]

Since the themostat and the AC control board are 12v I'd check for a dead battery first.

[oakland ironworker]

well I bypassed the wire running from panel to ac and it works. so the break is somewhere in the ceiling or wall. now to try an figure out how to fish a new wire in.

thanks for your help

greg