Wiper Switch or Motor

[Orange Truck]

My wipers do not work. Previously, it would work on occasion and would require activating the switch knob a few times before it would turn off and stop. Obviously the problem is in either the switch or the wiper motor. Is there an easy way to determine which is the problem before new parts are ordered. I do not want to end up with both a switch and a wiper motor when probably either one or the other is needed. Help! (To see the truck click on Orange Truck registered user name).