Variable Wiper Alternative

I would never use WD40 in a switch, it turns to sticky glue like honey. CRC electronics parts cleaner is what to use. If switch shorts there are likely loose terminals. With care rivets can be tightened and clear epoxy used to fix insulators. I made a repairs in the early 80s that still work today. I learned from my dad, almost anything can be fixed, and results can be better than new.

While the FSM suggests the motor reverses, it would take contacts to reverse the polarity on the field, or armature, not both. I am wondering if the exotic linkage results in reversal as the motor is turned off and torque reverses.

Mine still works, and I am getting too old to tear into it for curiosity.