1. Get yourself down to the local salvage yard.
2. Find any FoMoCo product with a dash mounted rotary wiper switch. I got one of mine from a mid 80's Ford F-150 Lariat and another from a Bronco XLT. 
3. There are two parts that you need to get: The switch itself and the controller box. The box is held on by either a tiewrap type set up or a small screw. The switch comes out by pulling off the knob and then unscrewing the collar behind it. The switch has a single black ground wire from it. You will need this ground wire, so if you cut it, or it is already cut, be sure that there is enough left to run to ground.
4. Pay for your treasures.

 

     Installation is generally easier than removing the unit was. I recommend that you test the unit prior to removing your wiper switch.

1. Unplug the wiring from your original wiper switch.
2. Plug your original harness into the black (female) receptacle on the controller. Ground the black wire from the new switch. Turn on the ignition switch and test your wipers. Center position is off. Full counter-clockwise is the longest delay, just before the OFF position is short delay. Clockwise from OFF is low and high, just like before. Push for washers.
   Note:
   If the wipers work on High & Low, but not intermittant - check the ground pigtail from the switch. The switch ground is a required part of the intermittant circuit.
   If your washers do not work, read the UPDATE below.
3. Once you're sure that the box and switch are working remove your old switch and install the new one.
4. Find a good ground and secure the single wire from the switch to it.
5. Secure the controller box somewhere out of the way. The box does not need to be grounded, so you can tie-wrap it, tape it, velcro it - whatever.
6. Enjoy your OEM intermittent wipers.

• The controller PN is "-17c476-". I have one E4ZB-17C476-xx and one E0ZB-17C476-xx, both work. The D2ZB- example in the illustrations is an original 72/73 Mustang part.
  

The original switch is on the left, the new switch on the right. Note the difference between pin outs. To correct this, do the following steps to the connector that goes from the box to the original wiring:
1. Locate the tab as indicated by the arrow in the picture below.


Connector as wired from Ford.
2. Working from the tab side, gently squeeze the sides of the tab to release the lock and pull the wire free of the connector. The picture below shows the pin removed from the connector. The arrow points to the spring tab that acts as the lock.


Locking tab on pin.
3. If you squeeze too hard you may bend the tab beyond the point where it can lock into the connector. If the pin does not lock into place in the next step, pull the sides of the pin with your fingers to open the gap a little.





Connector as wired for washers to work.

4. Install the wire that you just removed to the position indicated above. Slide the pin into the connector until it locks in place. Check the lock with a couple of gentle tugs. If the pin comes out of the connector go back to the previous step.

Plug the rewired connector back into the car and check the washers and wipers.

* If you have washers before installing the switch into the dash, or prior to installing the knob, but not after then you need to add a spacer (app. 1/4") into the wiper knob. This is because some of the switches have a shorter shaft than others.

* Remember, if the pigtail ground wire from the switch is not connected to ground you will have regular two speed wipers, but not intermittant.