Washer pump get's it's signal voltage from the wiper switch when it's pushed in. I'd check to see if there's voltage going to the pump. If there is, you've got a bad wiper switch, or shorted wiring.hey i have a 79 berlinetta. I can't seem to figure out why the windshield washer pump will not shut off. It is a new pump, and from what I understand, has a mechanical shutoff? Any advice is much appreciated, Thanx.