Note wires number 950 and 951 at the bottom right of the below image which provide power to the pump through the switch.
![Image](http://fordification.com/tech/wiring/wiper-delay-wiring_79truck.gif)
Wire 950 is the source wire to the early switch. Wire 951 is missing the terminal on the late model switch and plug. They run the switched power to the pump on the 950 wire. The fix is to squeeze the sides of the male terminal inside the connector and push it out the wire end, then place it back in the empty hole where the brack and green wire to the pump connects.
It's cold, my fingers are numb and if this doesn't make sense I'll try to take some pics and update the thread when it's daylight out and warmer.