Maybe you can 'see' it from when you disassembled the switch:
Park is powered with the switch off. The circuit is opened every revolution when the wipers are down. This happens in or under the white switch plate. It must also allow power to the field and the armature for that last sweep, and maybe it does so through the A to F connection in the switch.
I agree the resistor drops the field voltage and current. This may be the big difference between the various switches and motors. The simple assumption is the resistor reduces field voltage and current so must be low speed. But the snip you posted from a service manual suggests at least that model may work differently.
Park is powered with the switch off. The circuit is opened every revolution when the wipers are down. This happens in or under the white switch plate. It must also allow power to the field and the armature for that last sweep, and maybe it does so through the A to F connection in the switch.
I agree the resistor drops the field voltage and current. This may be the big difference between the various switches and motors. The simple assumption is the resistor reduces field voltage and current so must be low speed. But the snip you posted from a service manual suggests at least that model may work differently.
