The only schematic I could find was for the DR3 with self parking. Your DR2 may be similar. If you have a schematic showing the function of the switch and its connection to the motor... I'll scan what I have and send it to you for comparison.
On the DR3 one wire provides power into the motor. There are two sets of windings and the dash switch provides a ground path for one or both of these windings. On the DR3 the park switch is built into the cover. It provides a ground connection (like the dash switch) until the motor reaches the "park" position. In the case of the DR3 schematic I have, it shows the park switch connects to the high-speed terminal on the wiper motor.
Again, if you've got a schematic for your DR2 I'll scan what I have for the DR3 and send you a copy for comparison.