MTFCA Forum

Working away on the ignition switch wiring but have derailed myself.

I removed all the wiring screws but putting them back in the correct places is a problem.

I didn't realize that they are two different lengths so now don't know which what goes where.

Any hints on where longs and shorts go?

Many thanks,

Joe

I guess the answer might depend on your wire connection thicknesses and switch backing plate (original?). Likely the screws were replaced at one time but as long as they don't go all the way through it shouldn't matter. The BAT connection might need a longer screw because of the brass link but all the rest, the same. Your pdf show 6 screws and 5 lock washers

Over time the wiring could have been replaced. And if it was the exact screws may have been lost and replaced with what was available at the shop or could be found in the mechanics screw assortment. As long as the size and threads are correct for the switch the length needs to be long enough to hold the wire on the back of the switch.
If your replacing the wiring harness itself be aware the eyes on the wiring may not be exactly the right size as the original. The screw head will cover the original eye completely. Some of the replacement harnesses have eyes that are a little bigger but will work. It’s the eyes that are bigger around and the original screw head won’t completely cover it.

Factory print detail of part numbers for the wiring screw and lock washer used on the ignition switch.

Sizes from parts book price list complied by Bruce McCalley.

Great to see that the picture got posted. I've been trying all sorts of sizes and formats to figure out how to add the picture. Thanks for posting what I was trying to explain.

I did put out only 5 lock washers....there's another one around here that will be added to complete the team.

I believe that every part of this car has been changed somewhere along the way so these screws could easily be replacements that were handy.

While they are different lengths, Dan's detail shows 9/32" as the correct original length, so I'll head that way.

Many thanks for the collective wisdom.

Joe

Do not use screws that are too long, or the switch will not work smoothly and make good contacts. The brass lugs that the screws go in to, are "cupped" inside the switch. The "springy" ends of the "spider shaped" contact pieces are formed to seat into those cups when you turn your light switch or ignition key. If the 6-32 screws are too long, you will not feel the switch making good contact, because it will only be scraping on the ends of those screws , rather than seating into the recesses.
It is easy to shorten the screws. Most of the electrical crimping tools have the feature for snipping the screws.

Good information on the contact surfaces, Jim Sr.

I originally thought that the internal contact was with the screws so was concerned about the length being correct. Your comment and checking the ignition switch back plate detail in a vendor's catalog shows the contact cups on the underside of the plate.

The screws are just to hold the wiring to the plate and make contact with the plugs running through the plate.

What a wonderfully simple setup with such clever engineering behind it.

Turns out that screw length is not important except if too long and interrupting the internal moving parts.

Thankful to have this small but critical part sorted out...at least in my mind. Now to make sure the real thing is working as needed.

Many thanks, all.

Joe

You should also leave all the screw out, assemble the switch and try all positions and peak in the hole to ensure a good contact for the switch function.