1991 Dodge Dakota Electrical

It sounds like a problem with the multi function switch on the steering column. When you turn the lights on, power goes through the switch that runs both signals, high beams, and wipers. That is where I would start checking to see if there is a broken wire, short, or the switch itself is bad. It sounds like the switch to me. The power for the headlights is being fed to both the lights and the wipers.

Let me know what you find.

Joe