Check your fuse under the dash, then pull the wiper motor plug and check to see if you are getting power, remember the wiper motor has to be grounded to work, no ground, it won't work. If your test light isn't grounded it won't work either and none of the wires in the plug are a ground. The motor is grounded through the mounting bolts. Make sure they are clean w/o corrosion.
I would imagine it's one of those before i would suspect the int. circuit. I believe on that unit, the int is bypassed when the switch is in the on or high position... I don't have my books anymore...
90% of the time the switch will last forever, it's the motor that burns up...
The wiper motor in my Blazer was stolen off my truck right out in the parking lot at the local Meijers... Couldn't believe it.