2 switches, 1 light question

[InsanePyro]

Hey guys, got a question about the light at the top of my stairwell. It's the normal setup where, when everything is working right, you can shut off or turn the light on with whichever switch you want, the one at the top or the bottom. Recently, the top one seems to have gotten a little silly. When I flip it, the light will flicker when the switch goes past the middle...but the light will stay on regardless of the top switches position. The bottom switch is the only one that will turn the light on or off. Logic seems to say just replace the top switch but, I don't know much about AC so this seems like a decent place to actually learn something instead of just firing off the parts cannon and being happy when it fixes it. What do I need to do to actually diag this to maybe learn something to be better prepared for bigger problems?

 

[Wrench97]

It's probably a switch failing,
There are a couple different ways it could be wired depending if the power comes into the switch box or the box the light is mounted in.
Also older versions will not have a ground on the switch.

3-Way Switch Wiring Explained - MEP Academy

Learn how to wire a 3-Way Switch in different configurations including in a stairway. See how 3-way switches work.

mepacademy.com

 

[Chuckster in NJ]

Failing 3 way switch and I suggest replacing both of them. Easy to do……. Pay attention to the "dark colored screws" and replace one wire at a time.

 

[PCustoms]

@InsanePyro

You can carefully/slowly take the switch out of the box (probably best to turn the breaker off) and check for loose wiring or anything odd.

Take good pics of the wiring from all sides.

If needed we can tell you what switch to buy.

Then swap ONE wire at a time over. If you have an issue the pics can be the fallback.

It's not too complicated (usually) if you are methodical. But if you rip everything off, go the hardware store and come back an hour later with a bunch of wires sticking out then it gets tougher to ID what goes where LOL

 

[The Cobbler]

very likely the switch has failed. you need a 3 way switch, and as others have said, there's different ways it can be wired.
buy a new switch, take the original out of the box, take pictures from both sides showing the wiring ... post it here & someone will guide you thru it. maybe a good time to change the other switch while you're at it

 

[mm08822]

very likely the switch has failed. you need a 3 way switch, and as others have said, there's different ways it can be wired.
buy a new switch, take the original out of the box, take pictures from both sides showing the wiring ... post it here & someone will guide you thru it. maybe a good time to change the other switch while you're at it

Changing the faulted switch first and proving the repair works in all possible switch positions (of both switches) would reduce wiring connection issue possibilities. Only then, go for the 2nd one.

 

[The Cobbler]

just wondering if the other switch could be bad, in both travelers live ?

 

[InsanePyro]

just wondering if the other switch could be bad, in both travelers live ?

I don't think so, as it works perfectly, no flickering or anything, but I'll change both regardless, not like they're expensive. Can I test the switch with a multimeter or something? Not that its necessary but I'd like to come out with some actual knowledge not just "yup I can transfer wires"

It's not too complicated (usually) if you are methodical. But if you rip everything off, go the hardware store and come back an hour later with a bunch of wires sticking out then it gets tougher to ID what goes where LOL

I learned not to do that **** the first time I did an engine swap and didn't label a single thing. "Oh yeah, I know my Bronco, I'll remember"

I did, in fact, not remember a damn thing

 

[mm08822]

I don't think so, as it works perfectly, no flickering or anything, but I'll change both regardless, not like they're expensive. Can I test the switch with a multimeter or something? Not that its necessary but I'd like to come out with some actual knowledge not just "yup I can transfer wires"

I learned not to do that **** the first time I did an engine swap and didn't label a single thing. "Oh yeah, I know my Bronco, I'll remember"

I did, in fact, not remember a damn thing

Pictures are the savior for soooooooooooo many reasons. What's the worst that happens, you have to delete them?

I have shut some people up in nano-seconds with as-found and as-left pics. You never know when they become the ace-in-the-hole!

 

[The Cobbler]

the light will flicker when the switch goes past the middle...but the light will stay on regardless of the top switches position.

this is why I'm thinking both travelers could be hot all the time

 

[PCustoms]

Delete

 

[dscheidt]

I don't think so, as it works perfectly, no flickering or anything, but I'll change both regardless, not like they're expensive. Can I test the switch with a multimeter or something? Not that its necessary but I'd like to come out with some actual knowledge not just "yup I can transfer wires"

I learned not to do that **** the first time I did an engine swap and didn't label a single thing. "Oh yeah, I know my Bronco, I'll remember"

I did, in fact, not remember a damn thing

So a three way switch is basically two switches side by side. Turning one off turns the other on, and vice cersa. There are three terminals on the switch (plus a ground, which I ll ignore). With the switch up, two of them are connected. With the switch down, the other terminal is connected to one of the ones that were connected before. The terminal that is always connected is line, on one switch it’s always hot; on the other switch, it’s connected to the load. The other two terminals are called the travelers, they connect to the travelers in the other switch. When both switches have selected the same traveler, the two line terminals are connected, and the load gets power.

Make sense? Easy to ring out with a meter, and test if the switch is flaked out. One likely failure is that the switch is shorted, so that both of internal switches are always hot, so that the both travelers are hot regardless of what the switch is doing. It goes out in the middle because at that point both internal switches are disconnected. (It is break before make.). So pay attention to the color of the screw, because not all 3 way switches have them in the same places. Hot should be black, travelers gold.

 

[Chuckster in NJ]

I learned not to do that **** the first time I did an engine swap and didn't label a single thing. "Oh yeah, I know my Bronco, I'll remember"

I did, in fact, not remember a damn thing

Don’t try sky diving!

 

[dave*99]

Hey guys, got a question about the light at the top of my stairwell. It's the normal setup where, when everything is working right, you can shut off or turn the light on with whichever switch you want, the one at the top or the bottom. Recently, the top one seems to have gotten a little silly. When I flip it, the light will flicker when the switch goes past the middle...but the light will stay on regardless of the top switches position. The bottom switch is the only one that will turn the light on or off. Logic seems to say just replace the top switch but, I don't know much about AC so this seems like a decent place to actually learn something instead of just firing off the parts cannon and being happy when it fixes it. What do I need to do to actually diag this to maybe learn something to be better prepared for bigger problems?

There are dozens of videos explaining 3 way switch operation on Youtube.
Here is one example. They omitted the neutral connections for simplicity.

 

[wyliesdiesels]

this is why I'm thinking both travelers could be hot all the time

that would mean the other switch is bad since power on travellers comes from other switch

 

[The Cobbler]

that would mean the other switch is bad since power on travellers comes from other switch

just wondering if the other switch could be bad, in both travelers live ?

 

[dave*99]

I don't think both travelers are hot. If that were the case, his bottom switch would not turn the light on/off.

I think his top switch has failed. Perhaps the external toggle lever/handle is no longer moving the internal wiper from one traveler to the other. It's stuck on one traveler. When he moves the handle half way it disturbs the connection, the light flickers, but once the handle is fully flipped, the internal wiper stays connected to the same terminal/traveler as before he moved the handle..

Essentially the top switch is always on the same traveler regardless of the handle position. When the bottom switch energizes that traveler, the top switch has 2 ON positions. When the bottom switch energizes the other traveler, the top switch has 2 OFF positions.

 

[Milton Shaw]

I also mention that in different brands I have seen. Some of the travelers are all on one end and another brand they are all on one side of the switch. You need to watch and as others have said find the dark screw as that should be the power feed wire or the light power wire and the other terminals are the travelers. Then there is a four way switch that all the wires are for travelers to really confuse things.