Timing Circuit
This circuit consists of two diodes, a capacitor, a transistor, a holding switch located on washer pump, and a variable resistor in the dash switch. When voltage is applied through the resistor, the capacitor is charged. At a predetermined point of charge, capacitor causes transistor to switch, completing a ground circuit for the pulse relay coil. Pulse relay coil contacts close, completing the battery circuit to wiper motor. Holding switch contacts are held open by a fin on the washer pump drive cam. When wiper starts to run, fin is moved away from the holding switch allowing contacts to close. Two things happen at this point: The capacitor is partially discharged in preparation for next delay cycle, and transistor is turned off.
Also, a holding circuit to ground for pulse relay coil is provided until wiping stroke is completed. The cycle is repeated when fin on pump drive cam, re-opens the holding switch contacts at end of the wipe stroke, and again the capacitor starts charging.