The outside compressor spring loaded controller swich located under a metal protective cover became stuck and included failure of a air handler breaker. The same switch on another unit remains in the compressed position, and there is 27 volts flowing to the controler tranformer engaging the spingloaded switch yet the main breaker is off to the unit. The units are Lennox models
12ACB30-5P - Current flowing to switch, switch is depressed
12ACB48-5P - Blown air handler fuse, switch removed and freed of restricted movement.
That part is called a contacor. There's high voltage on an AC that comes from the breaker and ther's low voltage that comes from the furnace/air handler. Didn't see a question in there but hopefully that answers what you need to know.