1994 Dodge Caravan windshield wipers

Windshield wipers stopped working. Fuse is good. There is voltage on the center two pins of plug when switch is on but not on the outside two pins. I plugged in a new mortor and it didn't work either. (Motor was not installed. So not grounded?)
Is this likely a switch issue?
I need advice on properly checking the voltage at the plug so that I can narrow it down to the switch or the motor.