my husband looked over the wiring, and we won't be plugging this one in for a while - the insulation right where the wire enters the motor is gone and you can see bare wires.
This is a case where someone rewired - but they used wire too large in diameter and could not get it to fit correctly where it goes into the motor and the other switch housing. so they trimmed the outer coating back to just before the entry and ran the wires with no extra support into the housing. Since that is a significant flex point, the coating on the individual wires has worn off.