Technical single speed wiper motor

I have a '54 Plymouth Suburban with a single speed wiper motor. There are two wires going to the motor, and the wiring diagram indicates the housing is grounded.

Why two wires? Does the second power wire provide for homing of the wipers, after the switch is turned off, facilitated by a switch internal to the motor? And if so - why the need for a second switch terminal in the included diagram? Why not connect the homing wire directly to the "B" (input power) terminal? Confused...

-Dan

 

To answer some of your questions, one terminal (green wire) is used for P (park) on your switch.
The other terminal ( black wire ) is used for the single speed run mode.

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Yep^^^, otherwise it would just stop wherever it was when you shut it off, with the blades at any point on the glass, like it does if you turn the ignition off with the wipers running.

 

Understood. But, the dash switch can't know when the blades are parked - only the wiper motor apparatus can, and it interrupts the flow of power to the motor at the parked position. If the dash switch is on, the motor powers the blades through the parked position. If the dash switch is off, the motor stops at the parked position. For this to happen, P must continue to receive power from B, even when the switch is off (severing power to R).

In other words: B and P must be internally connected. Which, to my mind, begs the question: Why not put the P wire on the B terminal? When every extra bolt adds up to car manufacturers, why complicate the switch?

What am I missing?

 

Ah... I know what I'm missing! It's there in plain English: The circuit breaker. You can't interrupt power to the motor if the windshield's jammed with ice, if P is directly connected to B.

I'm good!

 

Sometimes just talking ourselves thru a problem we figure out the solution. Good job.

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