Wiper Motor Difficulties

[Steve R]

Gary,
No problem buddy. When I first started to try and understand how the Lucas wiper sytem works, I asked many people. They could tell me how to get it to sort of work, but I could not find anyone who could explain the whole thing to me, to my satisfaction. So one winter day I sat down with the motor, toggle switch, jumper leads and a meter at my kitchen table. ( I parked my car outside and ran a set of jumper cables from it through the kitchen window for power) I played with it until I had a good idea of how it operated. Then I got a piece of paper and a pencil and used my ohm meter to make a truth table for what the toggle switch does internally. I then devised the schematic to show that info.
I then dissasembled the motor and removed the plunger switch assembly. I made a truth table for that one also. then I devised it's schematic. I then made a mechanical schematic of how the cam on the gear interacts with the plunger switch.
Finally I put it all on the drawings you see here.

I still could not for the life of me undertand why they gounded the normally powered side of the motor's winding when in park. Many months later I happened to be thinking about that question (it was bugging the hell out of me) one day, While working on my friend's Classic Roadster I was messing with the pusher fans. (you know, the ones that came on the real cobras) They were connected electrically to each other but not to the car. I spun one fan with my finger and to my surprise the other one moved! OH, YEAH, the motor I spun acts as a generator when moved by an outside force. the power it made moved the other motor. Still fooling around with them I held one fan blade still while I turned the other one..... It was harder to turn. Hmmmmmm. Then the light bulb in my head went bright! thinking back to the wiper motor, I realized It's a magnetic brake when the windings are grounded by that plunger switch!!!!! They did it that way so the cam does not glide past the plunger.

I spent a lot of time to figure it out. That is why I don't mind sharing the info.
Steve