Why are wiper motors switched ground?

[davepl]

Does anyone know the historical reason why windshield wiper motors always seem to be switched ground instead of swtiched power like everything else?

I assumed it was for making the "parking" feature on hidden wipers, like on my 69 Pontiac, easier to implement. But in the other wiper wiring thread (didn't want to randomize it) they say that they've been switched ground going all the way back to single speed stuff.

So why not switched power? Being switched ground means they need those fancy isolated rubber mounts and various other complexities...

[VetteVet]

Possibly because multiple functions of a device are easier to control using a common ground rather than running several live wires and switches. The same holds true with the dome light and the ground switches that turn it on. I think mainly it was cheaper for the factory to do it that way.

The blower motor is an example of using positive switching for different speeds but the speeds are designed by using resistors instead of separate windings in the blower motor.
Just my theory but a very interesting question.

[SJLenz1340]

Switching a ground also creates less of a spark when switching inductive loads like motors. (2 cents worth)