[Robert Crandall]

I had that problem with my 1978. It took weeks of looking, but I finally figured out the problem is mechanical. There is a wheel with a cam that operates with the windshield wiper motor. You activate the washer, the wheel makes one revolution, and a cam turns the pump off. On mine the cam is worn, so instead of turning the pump off, it bypasses the pump switch, and the pump runs continuously. The only fix was to buy a new windshield wiper motor, which I will not do until I need one for the wipers. I let it pump dry maybe 20 years ago, and never filled the water bottle. It may still pump when the wipers are on.