[hiccup]

If you have voltage out of the switch going into the wires, but no voltage on the other end of the wires, then there must be a break in the wire. The wires typically go through at least one connector on their way from the switch to the wiper motor, so the problem could be in the connector(s). The wires also take some sharp bends along the way so it is possible that one or more of the wires has been compromised.

But also consider that depending on how you measured the voltage, it might be the ground lead that is the problem. I would measure with the ground lead on the battery or at least a known good ground point.