Here are several photos of a
1954/55 Chevrolet truck 6v 2-speed electric wiper motor. From looking at Bill's photo, it looks like the earlier 6v motor looks like the later 12v motor.
The motor, as Bill describes, can have two cables attached to it (see the last four photos). One cable is for the slide-actuated on/off/2-speed control; and, one cable is for the foot-actuated windshield-washer mechanism (it cleverly turns on the wiper-motor when the washer squirts on the windshield).
On the front on the on/off cable, there is a tab/clip which goes into the little "pocket" on the motor-housing. You can also see the grooves for two cables on the cable-attachment-point on the motor housing (there is a cable hold-down clamp/cover which is not shown in the photos
I'll post a photo of the on/off/speed cable/clamp, if you want to see it). You can see where the second cable attaches. However, I am not certain how the second cable (for washer/wiper) activates the wiper (maybe Bill or Greg Hill has a photo?).
