The basement got flooded this spring, only a few inches though and the electric parts of an air conditioning unit are a ways-up from the bottom. Still, it was possible water got in there and damaged something. I took the whole thing apart and all the electrical parts looked pristine. I disconnected the cord from the unit and sure-enough, it still popped the breaker even when separated from the unit.
I had a power cord from another air conditioner that died a few years ago and so I attached it and the unit runs fine now.
And yes, I do have some screws left-over now that the unit is all reassembled.