If it is what I think you need to seal the pigtail from the wipermotor at the plastic connection to the plastic plugin to the power. The pigtail extends about 6 to 8 inches from the wipermotor. Moisture gets into that connection and causes a short. Most common is they stay on and you can't shut them off or they stop and won't turn on. Once the connection is dry the wipers work normally. This was a common Workhorse chassis problem. A lot of folks just wrapped the connection with electrical tape to seal out the water.
Good Luck