The Stovebolt Site Forums The Shop Area The Electrical Bay 1950 3100 stop light switch?

Hello Bolters,
How can I test the original (Delco Remy) stop light switch while it's removed to see if it's still good? I do not want to replace if I don't have to.
Can I hook one wire one each lead and connect to my 6 volt battery and ?
Any direction would be appreciated.
Thank you.
Todd
////Update. The original Delco Remy switch works. Long story short (I'm no good with a meter) I hooked my taillight to my 6 volt battery with two wires going to switch. Works great. Thanks All.

If you hook each lead to your battery you will let all of the smoke out of your switch, and maybe start a fire.
You need a multi-meter set on OHMS. Attach the leads to each switch terminal and move the lever while watching the meter.
It is a momentary off switch, which means that on the bench, it will read "on" until you move the lever.
Carl

52,Carl,
Thank you. Will try tomorrow. Do the switches go "bad" ?

Yes they do but fairly rarely. 🛠

Ok, on " OHMS" It zeroed out then when I move the lever it goes up (300?) Does that indicate it's still good?
Thank you for the Help!!
T

If it is closer to the “screw side” no tail lights. If it is farther away from the tail light, lights come on. The lever should stay like the picture, Ie headlights on. Unless I accidentally say this backwards, you should have higher ohms when you push the lever to the “lights off position” and zero ohms when arm is extended (lights on).

https://www.ecklersearlychevy.com/e...ahPjsV0-fBmB29R_lwK0VxbE7CYaAsgPEALw_wcB

I would say that your switch is still good.

Chris

This is simply a toggle switch no different than the one on the wall for your house lights.
With the brake pedal up in the un-depressed or normal driving position it is holding the
switch lever back in an open condition.
When you depress the brake pedal, the switch lever is released by spring pressure to
close completing the brake light circuit.
A very simple basic OFF/ON switch.
and like any switch, the contacts can burn out, it can rust and get stuck or the spring can
break rendering the switch useless. If it is not working, and the stop lights come on when
you short across the two wires then the circuit is good and the switch is bad.

Denny Graham
Sandwich, IL

Denny,

Just to decrease confusion. He said that the ohms change from 300 to zero depending on lever position. Wouldn’t that mean the contact points are good on the switch if he is able to get different readings? The idea of “jumping” the wires to see if lights come on is a good idea. I never thought about that.

Well I don't have one off the truck and I'm not going to go out and disconnect mine to check it.
But..........common sense tells me that when open, it should read infinity and when closed
zero ohms.
If it 's reading 300 ohms in the closed position, that is a lot of resistance, then I would suspect
dirty contacts inside the switch. There is no way you would want to drop any voltage across
the switch.
dg

That's correct, when in the lights off position any basic ohm meter should read open, infinity or some cases 1- on the far left of the display. The lever should also move freely.
As mentioned above connect one wire to a good battery, then to either of the switches screws, another wire from the other switch screw to the center contact on a bulb, and the last wire from the building shell back to the battery. Operate the switch lever should toggle it on and off.

My bad, I thought 300 ohms was in open position (lights off) and zero ohms when it is closed (lights on). What is confusing me is when he talks about moving the lever, which way is he moving it.

if he moves it with brake pedal it will close it.
If he has it off the truck and moves it, it would open it.

Sorry, trying to figure out so I understand.

Shaffer, can you please describe how you are testing and which way you are moving the lever/switch? Some of us (me) aren’t smart but like to learn.

Chris

I apologise for the confusion. The brake light switch is on my bench (removed). With the setting on OHMS I tested the switch. The switch (I believe) when installed pushes that lever closed and when you press on the brake lever it opens (extends) the arm. So, that being said, when I hold the lever in the closed position (like it's mounted not pressing on brake lever) it is at ZERO. When I release the arm (like pressing on the brake) it goes up on the meter to about 300. Sounds likes it's working correctly.?

In this case, you are not checking ohmage per se, you are checking continuity. When switch is supposed to be off, meter should read "open". When it's supposed to be on, it reads some ohms or beeps. It does not make any difference how many ohms. You are not testing for proper ohms. Just to see if it has continuity. If it is passing current from one side of switch to the other. It is pretty easy to figure out which position is off and which position is on by mere observation of how it is mounted and operates. No reason to make this more complicated than it is. Continuity is usually tested with the component completely disconnected from any wires.
This switch is a lever operated, normally closed, momentary switch.

You can check it with the truck battery and bulb from truck. Don't need no stinking meter.

I am thoroughly confused. This is the on/off switch for the brake lights? When the pedal is not being stepped on, the switch is open preventing voltage to the lights, also called normally open. When the pedal is stepped on, the switch closes and allows the current to flow through the lights, momentarily closed. In the open state, the resistance is Infinite, in the closed state, the resistance is zero. Shaffer - verify the ohm meter is functioning correctly, test it by itself, leads apart should read infinite, leads touching should read zero. Then test the switch. whatever reading the meter gets by itself, should be the same as with the switch. Some meters have indicators other than infinite, and there may be a few ohm resistance between the leads, ymmv.

The "normally" part means what condition the switch is in BEFORE it is activated. This switch is activated most of the time when, as Denny says, pedal up, not pushing on pedal. But when the pedal is pushed the switch is allowed to spring to it's "normal", as in: on the bench, nothing acting on it, position. Which in this case is ON or "closed". So it is a "normally on", referred to as a "normally closed" momentary switch. It's a little confusing. When this brake switch is in it's normal position, it is in the electrically on position because it's contacts are closed. Normally closed (NC)
Example:
If you have a momentary push button switch, the button is always up. It's spring loaded, that's the momentary part.
If you hold it down, it can do two things. Turn on or turn off, a circuit. The naming convention goes by what it does when button is up, not being activated, not being acted upon. Being held up by it's internal spring. It's "normal" circuit mode.

The analog meter has infinity, meaning OPEN circuit as you said. The digital has a 1 or OL, meaning Open Loop, open circuit. Any ohmage reading or beep is closed loop or circuit has continuity. I don't know what the resistance of switch contacts is. I don't know what scale/range he is using. Milliohms? So 300 somethings is continuity. During testing of the meter itself, some meters will register zero when the two leads are touched, some will read the resistance of the leads if the scale is proper and it's a good meter. Reading zero is actually saying it sees continuity but not measureable because "I'm a cheap unit". Testing an actual component should always show some reading. Not zero. Or should beep, or show a reading and beep, depending on the meter.
Some multimeters have a continuity setting, some don't. Some have a buzzer, some don't. On some you just use the ohm section and select the lowest range so as to detect some ohms (continuity).
Some are designed to actually measure ohms and/or also to find the other end of a wire in a harness by listening for the buzz/beep.
You have to know what mode you are in. If you have an old style analog or new style digital meter and read the instructions.



Now I'm the one making it more complicated Man, I gotta get off this one quick............ Oh hey, it's also a single pole, single throw

Thank you for helping me wrap my head around this. I had to rush home and look under the hood, I had forgotten how the switch is implemented. Sure enough, it is being held open when the brake pedal is at rest. And “returns” to the normally closed state when pedal is depressed. Of course that concept has been covered several times already in this thread. So when the switch is not on the vehicle, it will be in the NC position and should read 0 Ω, as Shaffer has determined, but when the lever is moved (and spring tension is felt) the reading should indicate open. Shaffer states it reads 300, that is why it’s a good idea to test the meter by itself. Does the meter display 300 for open, or is the switch actually 300Ω when it should be open. If the switch is 300Ω when the lights are off, that may be enough resistance that the lights appear to be off, but there will still be current, and the battery will drain over time.

Testing your meter before using it on equipment is paramount, as bartamos stated. You need to know your equipment is working properly. He also covered using resistance or ohms function vs. Continuity ( sometimes denoted by a diode setting ), also important to know which is being used.

In the ohms or resistance setting a properly calibrated meter should read zero ohms with the test leads connected, or else it isn't worth using to actually measure resistance. On analog meters there was a knob to turn, on better digital meters there is a calibrate button.

If the meter being discussed is calibrated and being used in its resistance setting, then 300 ohms is not enough. As stated by waltervogel it will still have current flow. The reading should be infinite or Megaohms range depending on the meter.

Testing this switch is NOT rocket science. As Bartamos said you don't need a meter. I just did a quick bench test with my spare brake light switch using my spare 12v battery and a lead tester which has a 12v bulb. Hooked it up to the switch in it's relaxed bench position, meaning with brake pedal in force, the bulb lights up. move the switch's arm and the bulb goes off. Looks good to me. Obviously if you are still running 6v, test with a 6v battery and 6v bulb tester.