There's a new cam in town
Don't worry Duke, I'm not talking about the cam in the engine.
I'm talking about the cam in my 67 signal switch. Now that I have my second replacement switch installed and operating (as well as praying it will last), I thought I'd play around with my original switch and do a little article on the 67 signal switch, and it's cam, which is the guts of the switch.
Probably a good example of cost cutting, the Boyne signal switch used in 67 (and 68) Corvettes (as well as other GM cars through 69) was prone to mechanical failure and electrical problems. New in 67, it included the lane change feature, whereby one would just slightly hold the signal lever for a left or right lane change without having to turn the wheel to cancel the signal. It also incorporated the hazard flasher within the switch.
This switch by the 67 Chassis Service Manual was a non-repairable item. If you had a problem with it and took it for dealer service, they would just cut the ribbon cable at the connector at the base of the steering column, pull the old one out and toss it, and then thread a new one down the steering column.
But no, not this kid. I just couldn't bear cutting that cable on a original switch (also thinking about the cost of an NOS switch today). So with a little extra time, it was easy with a small screwdriver to remove the cable from the connector and pull it through the steering column. After doing this two to three times, I can now replace a signal switch, start to finish within a half hour.
Here's my original switch, showing what I think is the usual problem:
In the picture, the cam on the right has been removed from the switch (it just pryes off from the back side). As you can see, the two parts of the cam which hold the signal lever for a turn, and then cancel the signal, have broken off. The two metal spring strips are the lane change feature. They fit in a slot on the switch body, between the cam and the switch body.
If you spend a little time with an ohmmeter, and try to trace out the circuits, you'll realize that it has a pretty complicated circuit topology (as Jack H. would say). It has 4 input circuits, 3 of which go through the cam. Everything is hardwired or sealed on the switch, except the cam.
Being somewhat open, subject to wear and intrusion of dirt, the cam is the likely suspect for problems with the switch.
About two years ago, I figured I'd finally fix my original switch with a replacement cam from one of the usual Corvette vendors. The white plastic cam (with the markings SM-15), looked somewhat like the original cam. But after carefully soldering and heat shrinking the wires, and then carefully installing it while on the car, it didn't work. So I pulled the original switch off, and put on a repro.
Then a year and a half later, the repro went out. Seems I left the hazard flasher on too long, and the plastic around one of the contacts in the cam melted. So I put another repro switch on.
So I figured it's all in the cam, and began researching the cams. Finally found that Shee Marr corporation was just beginning production on a new cam produced from the original Boyne switch molds. So I ordered a couple to experiment with. It's the new SM-15 and it is red.
Here's a photo of the three cams:
The white one at the top is the one that didn't work. The main problem that I saw with it was the overall thickness of the cam and bosses on the underside, about a sixteenth in difference from the the original. Note in the picture, that the lane change spring strips are in position on the switch body.
The red one is the new SM-15. I haven't installed it yet but other than being red, it is almost exactly like the original:
So, tomorrow's another day. Stay tuned.
Having fun,
I'm talking about the cam in my 67 signal switch. Now that I have my second replacement switch installed and operating (as well as praying it will last), I thought I'd play around with my original switch and do a little article on the 67 signal switch, and it's cam, which is the guts of the switch.
Probably a good example of cost cutting, the Boyne signal switch used in 67 (and 68) Corvettes (as well as other GM cars through 69) was prone to mechanical failure and electrical problems. New in 67, it included the lane change feature, whereby one would just slightly hold the signal lever for a left or right lane change without having to turn the wheel to cancel the signal. It also incorporated the hazard flasher within the switch.
This switch by the 67 Chassis Service Manual was a non-repairable item. If you had a problem with it and took it for dealer service, they would just cut the ribbon cable at the connector at the base of the steering column, pull the old one out and toss it, and then thread a new one down the steering column.
But no, not this kid. I just couldn't bear cutting that cable on a original switch (also thinking about the cost of an NOS switch today). So with a little extra time, it was easy with a small screwdriver to remove the cable from the connector and pull it through the steering column. After doing this two to three times, I can now replace a signal switch, start to finish within a half hour.
Here's my original switch, showing what I think is the usual problem:
In the picture, the cam on the right has been removed from the switch (it just pryes off from the back side). As you can see, the two parts of the cam which hold the signal lever for a turn, and then cancel the signal, have broken off. The two metal spring strips are the lane change feature. They fit in a slot on the switch body, between the cam and the switch body.
If you spend a little time with an ohmmeter, and try to trace out the circuits, you'll realize that it has a pretty complicated circuit topology (as Jack H. would say). It has 4 input circuits, 3 of which go through the cam. Everything is hardwired or sealed on the switch, except the cam.
Being somewhat open, subject to wear and intrusion of dirt, the cam is the likely suspect for problems with the switch.
About two years ago, I figured I'd finally fix my original switch with a replacement cam from one of the usual Corvette vendors. The white plastic cam (with the markings SM-15), looked somewhat like the original cam. But after carefully soldering and heat shrinking the wires, and then carefully installing it while on the car, it didn't work. So I pulled the original switch off, and put on a repro.
Then a year and a half later, the repro went out. Seems I left the hazard flasher on too long, and the plastic around one of the contacts in the cam melted. So I put another repro switch on.
So I figured it's all in the cam, and began researching the cams. Finally found that Shee Marr corporation was just beginning production on a new cam produced from the original Boyne switch molds. So I ordered a couple to experiment with. It's the new SM-15 and it is red.
Here's a photo of the three cams:
The white one at the top is the one that didn't work. The main problem that I saw with it was the overall thickness of the cam and bosses on the underside, about a sixteenth in difference from the the original. Note in the picture, that the lane change spring strips are in position on the switch body.
The red one is the new SM-15. I haven't installed it yet but other than being red, it is almost exactly like the original:
So, tomorrow's another day. Stay tuned.
Having fun,
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