The power feed is supposed to be 240V, AC.
The power feed is actually 120V and the two legs are in phase.
Power out of the circuit breaker is fine and a vigorous 250V +/-1V.
There is a junction box on the outside of the house where the inside wiring is tied to the outside wiring which then runs through a conduit to the actual AC unit. They are connected via a pull-out interrupt.
A betting man would bet that one of the wires pulled out on the AC side of the interrupt and the bare wire end is touching the other side. Had the wire pulled out on the house side, there would have been a Ka-Boom and a tripped circuit breaker.
The only thing stopping me now is a rusty screw that was installed in 1977 that closes out the face-plate on the junction box. I sprayed it with penetrating oil but have little hope of breaking it free.
I am 90% certain that I am going to have to grind the head of the screw off to open up the box. Then, I will have to close it all up with a loose nut-and-bolt. That will be a job for tomorrow morning. Time is our friend when using penetrating oil.