Finding Out Why the Wiper Switch Does Not Work

Old Blue's windshield wipers stopped working in December while we were driving out to Point Reyes for a soccer game. The rain was light so it really didn't matter much and we do not plan to drive her in the rain but I was curious why they just stopped responding to the turn of the switch.

1966 F250 Camper Special Wiper Switch

Checking around the web I find some additional info regarding the '66 Ford Truck setup. Some '66's have the windshield washer switch integral with the wiper switch. Some (if equipped) have a separate push button washer switch above the ignition switch. Some have a foot activated floor mounted pump.

In 1966 both single & two speed wipers were available. If you can only turn the wiper switch one 'click' you have the Single Speed switch. If you can turn the switch twice it is a two speed switch. Old Blue has a 2-speed switch and pulls out which should control the washer function. However, Old Blue ALSO has the push button above the ignition key and it is wired to the the washer motor through the firewall but not grounded. I will have to check this out someday.

Removal:
It took a while to figure out how to remove the switch from the dash. Once you get it the procedure is quite simple, as follows:
1. Remove Knob : This is done by pushing a small screwdriver into the slot at the base of the knob, releasing the metal catch inside from the groove on the switch post and pulling knob gently off post. It took me a few times to feel the metal catch inside the knob with the screwdriver and to figure out how much pressure to apply (not much is needed) and when the latch slips the knob easily pulls off the post.

Slot to release catch

'D' shaped pressure catch inside knob

This same knob is used for other controls on the dashboard; I practiced with the heater control because it was easier to get to until I figured out where and how much pressure was required to release knob from the post.

2. Remove Bezel nut: I decided to remove the switch from the dash and then get underneath the dash to remove the wiring. the switch is seated in the dash by a simple slotted screw. I took a large flat screw driver and gently pushed counter clockwise on the slots - the screw spun right off.

Wiper switch bezel and retaining nut

The silver bezel marked 'Wiper' just lifted off the post and underneath the Wimbledon White paint was unfaded or marred. I could just imagine what Old Blue's dash looked like when she came off the assembly line.

I reached my hand up under the dash and gently pulled the switch and connected wires down a little so I could take a look at how they were attached.

You can see the 'gap' between the female connector and the switch housing

There are 5 wires connected to the switch and after looking carefully I notice the black parts are a male-female connector.

I gently encouraged (with my flat head screwdriver) the male connector out, turning the switch to expose three different leverage points and applying minimal pressure to each to move the parts (I was worried I might break the old, brittle plastic bits) until the switch fell lightly into my hand.

Turning it over I noticed how grungy and dirty it was and that the female wiring connector was loose from the switch housing. Leaving a gap along one side about 1/8" wide which I could close by pressing the wiring connector against the housing. It sprung back when I released the pressure. Hmmmmmmmm

Holding the switch in my hand, I could turn the post from left to right and back, feeling the two clicks but I noticed that when I pushed the connector against the housing the clicks were solid and when I let the pressure off the connector allowing it to 'gap' and then turned the post the clicks were almost non-existent.

Cleaning:
I shot the switch through the 'gap' between the housing and the connector with electrical contact cleaning fluid, worked the switch back and forth a few times and then repeated multiple times. I let it dry and then with a damp cloth wiped all the gook and dirt off the exterior of the switch. Moving the post again, the switch was moved much more freely now ...

While I had the knob off the post I thought I would figure out how to clean it. These knobs on Old Blue are ALL caked with a white substance that fills the grooves in the knob (see in pics above) and I have tried various cleaning products and brushes to get this stuff off the knobs but nothing seems to work very well.

Electrical Contact Cleaning Fluid 

The cleaned switch

I dipped the knob in water and took a toothbrush and brushed the grooves - after drying, the white stuff was still there. I took a wooden toothpick and ran it along the inside of the grooves - this removed the white gunk so I laboriously did this multiple times in EACH groove removing the white gunk and leaving the knob black and shiny. Sometimes elbow grease is the only answer ...

Mind The Gap:
I looked closely at how the connector was attached to the housing and saw 4 metal tabs on the housing that were pressed against the plastic edges of the connector. On the side with the 'gap' the 2 posts were loose from the plastic, allowing the connector to retreat from the housing. Taking a pair of wide mouth pliers I positioned the teeth of the pliers to just set on the metal posts, pressed the connector solidly against the housing and applied pressure - lots of pressure - to bend the little posts against the plastic. After a few times of doing this with both posts the connector stayed solidly seated  against the housing.

Re-seating the retention tabs to 'Close the gap' 

Re-Installation:
Putting the switch back into the dash was straight forward now that I knew how the various pieces fit together. I connected the wiring harness to the switch, fed it back through the hole in the dash, put the bezul on (there is a little nub on the back to help with alignment of the bezel) and screwed the retaining nut back into place using my screwdriver for the last bit to ensure it was tight. The knob slipped right back on and clicked into place.

I fired up old blue not knowing if I had fixed anything and moved the wiper knob to the right 1-click. The windshield wipers started moving back and forth - EUREKA !!!

I moved the switch to the second position and watched as the wipers picked up a little speed and then turned the switch back to the left and watched as the wipers gently glided to their resting place on the windshield. I repeated just for fun with the same results and felt lucky the problem was probably that the 'gap' allowed space to come between the metal sliding connectors inside the switch keeping them from completing the circuit OR maybe some gunk in the switch that had been blown out when I shot it with contact cleaner.

Information:
Once again Bill from the Ford Enthusiasts website has something to say about these switches:

C6TZ-17A553-B .. Two Speed Wiper and Windshield Washer Switch-7 terminals, includes w/shield washer switch / Marked: C6TB-17A553-B (Motorcraft SW-736)/ Obsolete

Applications: 1966 F100/350 from serial number 760,001 / 1966 F500/950 from serial number 802,001.

The serial number is the last 6 digits of the VIN, use this to verify the switch you need.

[This document shows how to remove the wiper switch from a Ford F250 Truck]