**They don't wipe much of anything but they do “operate”.**
The wiper motor must have a good paddle seal inside. Leaking vacuum causes reduced torque which causes the wipers to stop moving. It's like worn piston rings in an engine causing blow-by and reduced horsepower.
The weakness of good working vacuum motors is when the engine is under load and not producing enough vacuum. It's really not a fault of the wiper motor but a loss of vacuum. That's why Trico made the Electro-Vac.
Phak1, you have a typo. The business is called Ficken Wiper Service.
www.rebuildingtricowipers.com
