[davepl]

The motor is switched ground, so I'll presume the pump is too (easy to reverse the test if its not). Get a test light or DVM and see what you find at the pump wires before and while you turn the washers (only) on. If it powers the motor on the connectors, your switch is bad.

Be sure to check both sides of the circuit (power side and ground). At least one should change when you hit the washer switch. If its the same before and after, it's the switch.

If you replaced the switch, don't you have the old one around to just plug it into the harness (and ground the switch) to test it?

I believe the pump and motor are separate enough that I can't picture a short from one to the other causing the pump to run. If someone can come up with a scenario where it could happen, please throw it in here so he has the full range of possibilities.