a19593200,

Is there a chance you have them wired wrong. The dash switch supplies ground to the wiper motor to complete the circuit.

I think the button you are pressing on the motor is a overload relay. This also indicates something is wired wrong or jamming.

I have enclosed a link to a diagram that might help out. Good luck.

http://chevy.tocmp.com/1959_60shop/59sms1411.htm

Stuart