Replacement 2 speed wiper motors

Strange report....
I took a clean spare 2 speed motor that I had in the shed and tested it...It worked so I installed it....It made noise but wouldn't move the wiper linkage. It spun when under no load but with the linkage connected, it wouldn't move.
The original would start to move but then it would stop with the wipers pointing straight up.
I took the original and replaced the resistor, sandblasted and painted the motor and tested it. Now it works fine.
Who the heck knows what was wrong....Maybe a poor wire connection before, maybe the resistor was bad, I just don't know.
It is working now though so I'm calling it "fixed".

2 speed 5.jpg