The culprit in my 67 Turn Signal Switch

[Gerard F.]

About 3 weeks ago, I had a post and thread about no brake lights or hazard flasher lights. This was after I had gotten stuck on the road, and had had the hazard flasher on for about an hour and a half. Thought I'd update you guys on the outcome.

After numerous hours of trying to chase down the problem with a volt-ohm meter, the more immediate solution was simply to replace the turn signal switch. So I ordered a replacement one and after I received it, a couple of hours later, everything works just fine.

However now that I have the switch out and on the bench, I figured I'd track down what was exactly wrong with this switch. The switch in question is a replacement switch which replaced my original about a year and a half ago.

So I tracked down all the circuits in this switch and I pinned it down to the turn signal cam which distubutes the power to the various signal lights. I had continuity to the top of the cam for rear brake and rear hazard lights, but no continuity to the rear light feeds.

So I removed the cam from the switch by prying out the pivot from the rear of the switch. This is what it looked like with the cam removed and flipped over:



At first look, one would think it was the dirty and worn contacts in the switch itself, but on closer look and test with an ohm-meter, the real culprit pops out:



See that melted plastic at the connection of the top wire tang at the center. The melted plastic basically insulated the tang from the brake line connection which comes in the top of the cam. Just can't believe that leaving the hazard flasher on for an hour and a half could melt the plastic at this connection. Perhaps it was a manufacturing defect from the beginning, but the cam did work for about 18 months.

Here's my original cam for comparison:



You can probably guess why I replaced my original switch.

So now I'm scratching my head for a fix. Maybe a little screw and a washer or tang to bridge across the melted area. Maybe a new cam.
I have researched the replacement cams. I think most vendors have stopped selling the cam repair kits as they do not work. There is nothing I have found exactly like the original cam in configuration and thickness. I have tried a few.

You might see a Restorer Story, once I figure this out.

Having fun,

[Chuck G.]

Re: The culprit in my 67 Turn Signal Switch

Interesting, Jerry. Nice pictures too.

Although I have no personal experience with this problem, I'm aware that MANY have had problems with the replacement turn signal switches.

Chuck

[Walt W.]

Re: The culprit in my 67 Turn Signal Switch

Jerry, I purchased 3 replacement turn signal switches from different suppliers for my 67 and could not get any of them to work properly. They all said i was the only complaint they had heard of. The switches had wierd problems which would usually occur when manually canceling the switch. I finally found a NOS switch and the problems ended

Good luck with your project.

Walt Weems

[David D.]

Re: The culprit in my 67 Turn Signal Switch

Jerry,
Very interesting. From looking at the picture it 'appears' that the top wire actually fried and that was the cause of the melted plastic.
I'd be curious if you tried measuring ohms from one end of that top wire to the other? Or I'd suspect you already did and found it was just the plastic that melted and some how created an plastic open of sorts.....
David

[Joe C.]

Re: The culprit in my 67 Turn Signal Switch

About 3 weeks ago, I had a post and thread about no brake lights or hazard flasher lights. This was after I had gotten stuck on the road, and had had the hazard flasher on for about an hour and a half. Thought I'd update you guys on the outcome.

After numerous hours of trying to chase down the problem with a volt-ohm meter, the more immediate solution was simply to replace the turn signal switch. So I ordered a replacement one and after I received it, a couple of hours later, everything works just fine.

However now that I have the switch out and on the bench, I figured I'd track down what was exactly wrong with this switch. The switch in question is a replacement switch which replaced my original about a year and a half ago.

So I tracked down all the circuits in this switch and I pinned it down to the turn signal cam which distubutes the power to the various signal lights. I had continuity to the top of the cam for rear brake and rear hazard lights, but no continuity to the rear light feeds.

So I removed the cam from the switch by prying out the pivot from the rear of the switch. This is what it looked like with the cam removed and flipped over:



At first look, one would think it was the dirty and worn contacts in the switch itself, but on closer look and test with an ohm-meter, the real culprit pops out:



See that melted plastic at the connection of the top wire tang at the center. The melted plastic basically insulated the tang from the brake line connection which comes in the top of the cam. Just can't believe that leaving the hazard flasher on for an hour and a half could melt the plastic at this connection. Perhaps it was a manufacturing defect from the beginning, but the cam did work for about 18 months.

Here's my original cam for comparison:



You can probably guess why I replaced my original switch.

So now I'm scratching my head for a fix. Maybe a little screw and a washer or tang to bridge across the melted area. Maybe a new cam.
I have researched the replacement cams. I think most vendors have stopped selling the cam repair kits as they do not work. There is nothing I have found exactly like the original cam in configuration and thickness. I have tried a few.

You might see a Restorer Story, once I figure this out.

Having fun,

Great pictures, Jerry!
Poor contact = high resistance = heat, right?
If you decide to fix and reuse that switch, I'm sure that you'll double check and insure that every rivet retaining every wire on that POS is good and tight!!!!!!
Could it also be possible that the plastic is not as rigid as it should be, and is straining at critical points, causing poor connections>>>>>>>>high resistance>>>>>>>heat?
Can you refurbish your original switch, or use its plastic body as a donor?
Can you get a yob at M & H, or LL?

Joe

[Jean C.]

Re: The culprit in my 67 Turn Signal Switch

I had a problem with the repop switch I installed in my '64, it lasted about 18 months when it would not "set" for a left turn. Replaced it maybe a year ago with a switch purchased at the local Chevy dealer and it is working fine so far. Of course the General gets a bit more $$ for his.
Best regards

[Edward S.]

Re: The culprit in my 67 Turn Signal Switch

My switch went a few months ago and a friend of mine had his go a few months before that - I had remembered he had quite a time finding a repro that had correct colored wires. Based on what he ran into I ordered a switch from Paragon installed it and so far have had no problems.

[William C.]

Re: The culprit in my 67 Turn Signal Switch

Believe it Jerry, the looks of the plastic around the rivet is definately an overheat of the plastic, not a manufacturing defect. I wonder id the repop uses the same material as the original?

[Thomas H.]

Re: The culprit in my 67 Turn Signal Switch

Believe it Jerry, the looks of the plastic around the rivet is definately an overheat of the plastic, not a manufacturing defect. I wonder id the repop uses the same material as the original?

Jerry,
Once the rivet is installed, the plastic is they only thing maintaining the pressure on the contact between the rivet head and the wire. Once the junction starts to heat up (due to the resistance of the junction as Joe pointed out) the plastic will start to soften leading to decreased pressure between the rivet head and the wire, leading to increased resistance, leading to more heat...... eventually leading to failure.

Looking at the pictures of the repo vs the original, two things jump out at me. One is the material is obviously different. I'll bet the original is a higher temp material. The other is that the original rivets provide more contact area with the wire which reduces the resistance of the junction.

A better design would possibly have a metal bushing that the rivet goes through and the wire would be compressed between the bushing and the rivet head thus eliminating any plastic deformation from compromising the electrical connection. Hmm.........


Tom

[Timothy B.]

Re: The culprit in my 67 Turn Signal Switch

One thing I notice is the material the rivet is made from. The repro switch has a brass or copper plated rivet while the GM part looks to have a aluminum rivet, that may be for a reason as aluminum dissipates heat much better.

I am not sure how long this switch has been discountinued but I recall waiting a long time after ordering it from GM in 1987-88 when my 67 needed one.

[Michael F.]

Re: The culprit in my 67 Turn Signal Switch

The wire & rivet need a better connection. Heat from a regular solder gun would also melt the surrounding plastic. There are now battery operated soldering pencils that are advertised as operating cold. I wonder if that would work.

[Gerard F.]

Here's the fix

Tim,

Your comments gave me the fix.

I drilled out the brass connection, dug out the wire tang from the melted plastic, cleaned it up, and then put it back in place with an aluminum pop rivet:



Looks a little rough as I filed down the head, but it works.

Got the switch back together and all operations now have continuity where they should. But I'll wait until the other one on the car breaks down before I swap it.

Now on to my original switch. Wish I could find a correct replacement cam. The red one in these photos is an exact molding of the original white translucent one. Too bad they made it out of low temperature melting plastic with brass rivet connections.

[Jim S.]

Re: The culprit in my 67 Turn Signal Switch

Jerry,
I forwarded this posting to a switch engineer at Saginaw Steering. Unfortunately with Delphi in bankruptcy and Saginaw trying to be sold off, we might not find an engineer interested in looking at a 40 year old switch design problem. (Particularly since I think you mentioned that this was a repro part.)

We'll see if I get a response.

Jim

[Wayne K.]

Re: The culprit in my 67 Turn Signal Switch

Here's my original cam for comparison:



You can probably guess why I replaced my original switch

Jerry,

I remember reading somewhere that one of the causes of that part of the cam breaking was when using the signal lever for lane change not to go as far as the lever goes such that the lever stays like when you are going to make a turn. Manually forcing the lever back is harder on it than letting the steering wheel return it. I believe 67 was the first year for the lane change feature.

Wayne

[Gerard F.]

Re: The culprit in my 67 Turn Signal Switch

Righto Wayne,

67 was the first year of the lane change feature which makes the 67 switch different from the other C2 switches. The same switch was used in 68, although changed to a different (more lasting type?) in 69 and later.

The holdback ear on the cam was probably the first thing to break, for the reasons you said, and especially in cold weather.

The lane change feature was actuated by the two metal spring strips you can see in the picture above, on the switch itself. This makes the cam different from other replacement cams normally sold by vendors.

I just got a line on a brand new replacement cam just coming out that I think is correct for the 67-68 switch. Will let you guys know once I get it and test it out.