How to install a variable speed wiper switch into a
1971-1973 Mustang
This mod is for people that want to modernize their car and not keep it original.
1971-1973 Mustangs came with a 2 speed wiper switch.
CJ Pony Parts sells a Variable Speed wiper switch (part # WWS8) that fits the 69-70 Mustang. This switch will fit a 1971-73 with a little modification.
Note: I have replaced my original wiring with an aftermarket wiring harness. I had to add a jumper wire on the back of the original wiper switch plug to make the switch work. Please try the switch first in your car without making any cuts.
I used a 1972 Mustang Convertible as my test car; other 71-73 Mustangs should be similar.
Tools Needed- Drill
- 1 ¾ inch (44mm) holesaw
- File
- Hacksaw
- Phillips Screwdriver
- Needle Nosed Pliers
- Tape Measure
Figure 1: New and Old Switch
The main difference between the two switches is the length of the shaft.
I took a new and old switch apart to see if I could just modify or replace the shafts, but I could not. They are not interchangeable.
I removed the old switch and switch housing out of my 72.
Tip: If you do not have the proper tool to remove the bezel nut, you can use a pair of needle nosed pliers if you are very careful and the nut is not too tight.
Figure 2: Front of Switch Housing 
Figure 3: Rear of Switch Housing 
Figure 4: Old Switch 
Figure 5: New Switch
A 1 ¾ inch hole needs to be cut into the back of the switch housing to extend the shaft out the proper distance.
Figure 6: Switch Housing with Hole Placement Marked
Figure 7: Housing with Hole Cutout
I had to use a 1 ¾ inch holesaw to cut out the hole. As most of my tools were still in moving boxes, I had to make do without a vise and drill press.
I stuck a nozzle from a tube of caulk into the original hole so that my drill bit for the holesaw would not walk around while cutting the hole.
Pretty Primitive Pete, but it was all I had at the time
J
A small notch needs to be filed out in the wire bracket to let the switch sit flush.
Here it is marked out in red.
Figure 8: Location for Notch 
Figure 9: Notch Cutout Here is a picture after I cleaned it all up and painted it.
Figure 10: New Modified Switch 
Figure 11: Old Switch
Now one final piece needs to be cut.
The nut used to hold in the switch is now too long and needs to be cut down.
Figure 12: Old Bezel Nut
Install the new switch and bezel with the original nut.
Measure the amount that needs to be cut off.
Figure 13: New Switch with Old Nut
Figure 14: Nut after being Cut
Cut down nut.
Install new switch, housing, bezel and nut into car.
Plug switch into original wiring and ground wire according to directions.
Enjoy variable speed wipers
Figure 15: Final Installation
How to install a variable speed wiper switch into a 1971-1973 Mustang 
