I have a bad breaker on one of central ac units. However there are no labels on the panel to identify which breaker goes to what. How do I tell which breaker goes to the ac unit that has no power. I installed a new switch in the attic and measured the amps on the wires coming from the breaker while I had the switch off and got no voltage. I appreciate any help.

Thanks,
Mark

You need to use a voltage tester on each breaker. You state you measured amps and got no volage. What do you mean by this? How would you measure amps and expect to see volts?

Take the panel cover off and test the breakers, which should all be "on". You'll need a voltage tester or a "wiggie". Any breaker that is on but does not give power to the wire should be considered no good.