1930 stop light switch

Smokedtires

Smokedtires

Senior Member
Hello all, I am stumped on my brake light switch. It appears to be a closed circuit when brake pedal is not depressed, then open circuit with pedal pressed. Looking at a 28-29 switch it looks like the circuit is open at rest and closed in use. Is this correct?

Drawing should help demonstrate my explanation when not using pedal and brake lights should be off.
 

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Testing my brake light switch, the lights are on with the circuit closed at rest. Am I missing something, this doesn't make sense to me?
 
On a 1930, when the brake pedal is up (relaxed) the rod from the brake pedal pushes on the plunger of the brake light switch and opens the circuit. When the pedal is down (depressed) it allows the plunger of the brake light switch to move forward and close the circuit. When the switch gets grungy or rusted the brake pedal rod may move forward but the plunger may stick, and therefore not close the circuit. Or the plunger may move but not close the contacts. The brake lights won't go on. Likewise, if the brake pedal doesn't travel to the completely "up" position when you stop pressing on it, the brake lights will stay on.

Repod brake light switches aren't really consistently up to snuff. The original brake light switches had brass bushings where the rod entered and exited the sheet metal housing. Repod don't necessarily have those bushings. You are likely better to find or rehab an original than replace it with a repod.

You may be able to "rejuvenate" an old brake light switch by grabbing the back of the plunger and moving it in and out while twisting it vigorously, accompanied by blowing compressed air along the plunger and through the housing. This is similar to how we used to "clean" old radio volume controls back in the day (spraying liberal amounts of freon contact cleaner, now gone to the dustbin of regulation). If you get real ambitious you can pry the tabs off the switch and expose the internals, then polish the internal contacts with some sandpaper. They're really pretty simple devices.

I haven't played with a '29 brake light switch in many years so I don't recall how they work.

If your lights stay on, it sounds to me like your brake pedal rod is not opening up the circuit. That may be due to stickiness in the pedal travel (may folks have adopted the habit of hooking their toe underneath the brake pedal and pulling upwards after using it), or maybe the rod has slipped off the end of the switch plunger (that happens too). I'd suggest a trip underneath the car, or pull the floorboard, to look at that and see that it's functioning as intended. Sorry I'm not closer to NY or I'd come by and look at it with you ;-).

Good luck.

JayJay
 
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The 30-31 switch is a "normally closed" switch. So sitting on your bench, yes, the circuit is closed.

The 28-29 switch is "normally open". So, once again, when sitting on the bench the circuit is open.

The difference is in the installation. The normally closed 30-31 switch is installed on the crossmember and held open by the flat end of the brake actuating rod that connects the pedal to the brake cross shaft. So with your foot off the brake pedal the switch is being held open.

The 28-29 switch is installed in it's normally open position, it is mounted on the transmission tower behind the brake pedal. Pressing on the brake pedal then pulls the switch closed.
 
1955cj5 said:
The 30-31 switch is a "normally closed" switch. So sitting on your bench, yes, the circuit is closed.

The 28-29 switch is "normally open". So, once again, when sitting on the bench the circuit is open.

The difference is in the installation. The normally closed 30-31 switch is installed on the crossmember and held open by the flat end of the brake actuating rod that connects the pedal to the brake cross shaft. So with your foot off the brake pedal the switch is being held open.

The 28-29 switch is installed in it's normally open position, it is mounted on the transmission tower behind the brake pedal. Pressing on the brake pedal then pulls the switch closed.
Click to expand...
Thanks, 1955 - we violently agree.

JayJay
 
Thank you both, that makes sense. Sounds like some brake switch rod adjustment is in order to open the circuit "at rest".
 
Smokedtires said:
Thank you both, that makes sense. Sounds like some brake switch rod adjustment is in order to open the circuit "at rest".
Click to expand...
Recognize that "at rest" means in the car, not on the workbench. The switch will be closed "at rest" on the workbench, but open "at rest" in the car.

JayJay
 
If you have one of the cheepy versions, you can make it into one of the $50 versions with little effort. I did a write up a while back and posted it to several places.

Regards
Bill
 

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Bob C said:
How about using a flange bushing.
Click to expand...

You'll need to install the rod or something else inside the bushings to keep them in correct alignment while soldering them which would be more of a heat sink than the brass tubing. Also you'll need to make sure you don't accidently solder inside the bushings, or solder the rod in the bushings.

Anything is possible, but using the tubing seems much simpler.

Regards
Bill
 
I agree in that it’s a great write up Bill. Thanks for doing it and thanks to all of you who do similar!!
 
Hey guy's

Thanks you.

I removed the previous PDF and uploaded a much better version. If you want, go D/L the newer PDF.

Regards
Bill
 
I installed a new switch from one of the vendors, but it ceased to function within 2 months after installing it. And yes, it's one of the cheapies. It doesn't squeak and squeal as described above - it just doesn't work! :mad: Worked fine for several weeks and then - nothing! Guess I'm forced to buy one of the U. S. made units if I want it to actually work. My question is what's different about the inside the high dollar units that makes them cost so much more?
 
mcgarrett said:
I installed a new switch from one of the vendors, but it ceased to function within 2 months after installing it. And yes, it's one of the cheapies. It doesn't squeak and squeal as described above - it just doesn't work! :mad: Worked fine for several weeks and then - nothing! Guess I'm forced to buy one of the U. S. made units if I want it to actually work. My question is what's different about the inside the high dollar units that makes them cost so much more?
Click to expand...

Open it up and look inside to if it's functioning properly. You might need to adjust it. There really isn't anything to burn up. The difference is the $$$ has bushings.

Regards
Bill
 
BillCNC,
It would certainly be worth cracking it open to see what's going on before shelling out $57.00 if it's something simple.
 
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