Windshield Wiper Pump Problems

[cleszkie]

When I push my wiper knob to clean the winshield, the wipers come on and the pump pumps. That is all good But the pump does not stop pumping on its own like it is supposed to. I turn the wipers off and the pump stops. When I turn the wipers back on, the pump will start pumping again on its own I thought it was a problem with the wiper/pump switch, so I replaced mine with another Delco unit that did the same thing. So now I'm thinking its some sort of relay that is stuck closed in the pump unit itself. Can anyone shed any light on this situation for me? Is there a relay to replace, or do I need a whole new pump? Thanks in advance.