Troubleshooting 3-Way Switches: Why Does My 3-Way Switch Only Work Sometimes? (2024)


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Troubleshooting a non-working 3-way switch can be a reasonably large pain in the rear for any electrician or electrical contractor. In the latest episode of Electrician U, Dustin gives some Journeyman’s tips (well a Master’s tips really!!) that will make the process easier.

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So, you have a 3-way switch that only works from one side when the other switch is in one position or the other. In other words, if one switch is in the up position, the other switch will turn the light(s) on and off. But if you flip that other switch to the down position, the light(s) won’t actuate at all. This generally means that you have the travelers crossed and either the incoming hot or the outgoing switch leg on the wrong screws. A relatively easy fix once you can understand how a 3-way works and can visualize the process. PSA- always turn the power OFF before working on any electrical installation!
First, put on your troubleshooting/service electrician hat (figuratively of course!). A good tip- as you are unscrewing the device and pulling it & the wires out of the box, do it gently and slowly. A non-working 3-way may not be a miswiring issue as the source of your power issues but may in fact be loose wiring connections. If you pull something out to fast, you can change the state of the wiring and end up chasing ghosts! When you do get the device/wires pulled out of the box, check the connections on the device to make sure they are nice and tight. When putting switch/wires back in box, be careful not to pinch wires and make sure the bare ground wire doesn't come into contact with any of the screws on the device (with the exception of the green grounding screw of course!).
You may also want to check the wiring colors attached to the different color device screws. 3-way switches have 4 screws. A green one for the ground, a black/dark bronze one for either the incoming hot or the outgoing switch leg, and 2 brass/gold-colored screws for the travelers. Try to keep in mind that you will be bringing IN the power in one switch box and OUT to the fixture in the other box. Either of these locations will generally be done in a single 12-2 or 14-2 cable. The travelers (the wiring going in between the switches) will generally be done in a single 12-3 or 14-3 cable. So, the cable with the single black wire will go to the black screw on the device and the cable with the red and black wires will go to the brass/gold-colored screws. If you happen to see the single black wire attached to a brass-colored screw, then the travelers are crossed and that will generally be the source of your problem!
Depending on length (either the homerun or the traveler length in between the 2 switches) you may have to run the incoming hot and the travelers in #12 but the final switch leg up to the fixtures can be run in #14 (if it is a 15-amp circuit). So, another tip can be to look at wire size. If you look into the switchbox that is being used as the last box before it goes up to the fixture itself, if you see a #14 wire attached to a gold-colored screw, chances are you have something crossed.
In addition to the internal composition of the switches, you may notice that a 3-way switch does NOT have an ON/OFF label on the switch. Due to the alternating nature of the switches and being able to actuate from 2 different locations, they will change position each time you go in/out of different doors.
We hope this has been helpful in understanding how a 3-way switch works and some of the troubleshooting techniques to correct a non-working installation. Do you have a topic you would like to see discussed on Electrician U? Leave a comment in the comments section and let us know! please continue to follow Dustin and Electrician U as we are constantly updating our content to assist our followers in becoming the best electricians that they can be.

#electrician #electrical #electricity #troubleshooting #3-way #switches #electrical contractor


All right, I, just put a new three-way switch in.

And for some reason it doesn't work sometimes, but it does work other times.

Why is this happening [Music] all right? So I had a really good question asked to me.

This actually happens quite a bit if you're out in, uh, you know, like putting new devices into a home.

And you guys are just kind of ripping through and somewhere along the line, somebody miswired one of the switches so it's kind of indicative.

Usually if you have a three-way setup, where like one side doesn't work, the other side will so you'll, just flip it into the other position that changes the nature of power being sent over to this one.

And now this one will work.

But the problem might not be on this hot side, I have my incoming hot, then I have Travelers, and then I have a switch leg that goes up there.

So hot side is incoming.

Hot switch leg side is the leg side that goes up to the light.

So if you have some of the conductors on the leg side switched normally you're, just going to notice a problem with the one light source, or like the group of lights that you're working on a lot of times on the hot side, if there's a problem you'll, notice, when you switch something on an entire room will switch on or like multiple rooms might turn off or turn on it kind of depends on the situation, not always, but a lot of times with the hot.

Sometimes somebody will have wire nutted something together.

And then now they're, instead of passing the hot through the box they're using the device mistakingly they're hooking, the hot up to the device.

So the connection for the the rest of the circuit only happens.

Once you flip the switch into a certain State, when you flip it back, if there's no longer a connection through to the rest of the circuit that's, not only a hot side thing or only a leg side thing, I'm, just saying a lot of the times when you realize that when that's happening when you see multiple rooms, I tend to just go to the hot side, first because I know a lot of times they did something with the hots.

And then on a leg side, A lot of times it's, just this Source again, there's 50 ways to wire stuff and that's, not always the case.

So you could have one or the other.

So how do we go about fixing something like this? So you kind of have to pay attention to what's happening between the two switches so it's kind of indicative.

When you have this side that will not do anything, you know, this is the side that there's a there's, a something's being affected too.

This is probably not where the problem is it's, probably not being sent power for it to be able to change States again, not always there could be some weird stuff going on.

But my feeling about this situation is that when I go to this side and I, all of a sudden change it.

Now everything works over here.

So I'm like okay, this seems like it's, fine it's, just that when this is sometimes doing something different it's, not okay.

So my bet is that the problem is over here.

So what I'm going to do is first go, turn the breaker off.

So I can take this apart.

Look at it.

See if it's something switched put it back together and we'll see if it works all right now that the breaker's off I'm going to go to my leg side again, that's, just where I've got a hunch foreign I, actually love this little thing because it's only one speed it's just for taking screws out it's.

So light, it's, tiny, I can stick it in my pouch like, uh, you don't need.

This monster drill that you're carrying with you all the time if I'm not like drilling into something trying to pop holes or drill through masonry, I, don't need a big clunky drill on me, I, keep this little thing and I love it anytime that you take a device out you don't want to just like rip the thing out you want to look at it first and be like, okay, well, I know, there's, nothing going weird, there's, nothing like loose, because sometimes loose terminations make things happen as well.

And then you slowly, when you're troubleshooting always very slowly, pull everything out it's, not because you're going to get electrocuted.

I mean, you could I.

Guess you should get shocked, maybe, but you don't want to change the state of whatever is happening.

So you always want to look around very slowly, take everything out.

And once you realize, okay, me messing with this device is not going to change the problem or change the state of the problem.

And now I'm chasing a ghost then I pull the whole thing out.

So what I've got here is I've, got one conductor going on a gold.

Screw and I've got well, I've got a red already on my black.

So I know that there's something screwy there, a Red's gonna be a traveler, the Red's not going to be a hot or a leg again, could be depends on how somebody wired something.

But already that's kind of like suspect so I've got two black Travelers and a red on my black.

Screw so I have a three-way switch works is on the back side of this.

You can kind of think of like a flapper in there that's, not how it works internally it's like a it's a different thing.

But the way that I conceptualize, it is I like to think that there's a piece of metal going across here when the switch is in one position.

And when I switch that switch into another position, the flapper goes like this and goes, boom and connects these two.

So all a three-way switch is doing is just going? Boom, boom, boom, boom, that's.

Why we call this the common screw because this is the one that has everything in common.

So when you switch it into any state, this one is always a part of the the situation.

These two are not it's, switching back and forth.


So another thing that we can look at is well.

This is a 14 gauge conductor it's a lot.

You know, like skinnier.

These are 12 gauge conductors.

So these are probably in the same 12, 3 sheathing.

And therefore they should be Travelers.

So that's, my that's, what I'm suspect of the other thing is always look at the sheathing.

So back here, I've got one black coming from 1, 14 2 and I've got two 12s black and red that are coming from a 12 three the same sheathing.

Your Travelers are always going to be in the same sheeting.

They should be unless you have some kind of tricky crazy, illegal little three-way, dead end, three-way Chicago, three-way like weird stuff.

It could be weird stuff.

But if you know that this house was wired by y'all and it's like present times and there's, nothing weird old 50s, wiring then it's, probably that you just got these mixed up.

So I know, first and foremost, okay, I've got two Travelers here.

My two Travelers should be my gold screws.

And my 14 should be the one that goes on my black, screw because that's, the switch leg, your switch leg and you're hot on both sides of a three-way.

This is your hot side.

Your hot is always going to be on the black screw on this one.

And your switch leg going up to the light is always going to be on your black side on this this device.

So let's just switch these two around, pretty confident that this is going to be the problem I'm so confident, in fact, because I actually set this problem up myself, I know, this is going to work, but I'm gonna act really super surprised for y'all all right now.

Get it all magically foreign [Music], ER back on.

And before this thing did nothing, oh man, look at that.

But what happens when we flip it into the other state? Well, it still comes on I wasn't doing that before.

So now everything works no matter.

What if you flip it on, you can flip it off here.

If you flip it off, it actually comes on, but then you flip this one on so you'll, also, notice with three-way switches, there is no on or off State it's, always changing.

If you start in one end of the room and you come in, and you the lights off we'll say and you flip it, and you go to the other side and you flip it off.

And then you walk back through notice it's completely changed now.

So now, when you flip it up it's on when you and you just keep doing that now, it's going to go on now it's going to go off well, not off up.

But a lot of people are like, wait.

The switch is upside down.

No it's.

Not three ways are always going to change.

If you continually go in one side and go back out the uh, the same way then they'll always stay like the same.

But once you go in one side and out the other and then come back around it's going to keep like changing states, which is why none of the three-way switches say on or off on them like a single pole, switch does there's, definitely an off and definitely an on so that's.

It hope that helps you out in the field.

Stop wiring stuff backwards.


You crazy.

People see in the next one.

Troubleshooting 3-Way Switches: Why Does My 3-Way Switch Only Work Sometimes? (2024)


Why does my 3-way switch sometimes not work? ›

Sometimes, a 3-way circuit doesn't work because someone tried to replace a defective switch and did not properly connect the wires. Sometimes, one of the switches has become defective.

Why does my light switch only work sometimes? ›

This often indicates that the metal parts inside the switch are wearing out and that its contacts are failing to make the connections needed to complete the electrical path and allow the light to illuminate.

How do you tell if a 3-way switch is bad? ›

Locate a Bad 3-Way Switch

Usually when a 3-way switch fails, lights can be toggled on and off at one switch, but not the other. If one of the two 3-way switches toggles the light(s) on and off, the other 3-way switch has probably failed.

Why does my 3-way switch only work one way? ›

If a 3-way switch is wired incorrectly, this can cause several issues. The most common problem is that the switches will not function properly: Either both switches won't work, or only one will. Another issue is that one switch will trigger a short circuit, tripping the circuit breaker.

Why does my switch not turn on sometimes? ›

To fix a Nintendo Switch that won't turn on, try giving the battery a nice long charge. Check the Switch or AC adapter for damage, and make necessary replacements. Resetting the AC and Switch adapter can turn on your switch and allow it to take a charge.

Why is my light switch not working consistently? ›

Check the Circuit Breaker; Shut Off Power

A switch circuit that doesn't operate correctly may simply have a tripped breaker or blown fuse. Head to the electrical service panel and locate the breaker or fuse. If the breaker is tripped, reset it; or if the fuse is blown, replace it with an exact duplicate.

Why would a light stop working then start working again? ›

By far the most common problem is a loose wire connection at the switch itself, which is subject to constant on-off usage. Less commonly, a light bulb socket may go bad. If so, you will need to replace the socket.

How do you know if you have a bad light switch? ›

If you find that your light switch toggle starts behaving differently than usual (i.e. becoming stiffer than usual or losing its “snap”) it's a good sign that the switch mechanism is worn and should be replaced immediately by a qualified electrician.

How do I know if my network switch is bad? ›

To verify that your switch is properly working, check the LED lights located at the back panel of the device. They should be lit up to confirm that it is working. By performing a loopback test, you can also confirm that the switch is working. Before performing a loopback test, make sure that the device is powered ON.

What is the rule for 3 way switches? ›

As a rule, we must always install 3-way switches in pairs, and then as many 4-way switches as necessary. For example, if a light is to be controlled from four different locations we would need two 3-way switches and two 4-way switches.

Does it matter how you wire a 3 way switch? ›

It doesn't matter which traveler wire (red or black) connects to which traveler terminal as long as it's the same in both switch boxes. For example, if the red traveler wire is on the top traveler terminal in the first box, it should also be on the top traveler terminal in the second box.

Why does my 2 way light switch only work when one switch is on? ›

Incorrect Wiring: If the two-way light switch is wired incorrectly, it may only work in one direction. This can happen if the wires are not connected correctly or if the switch is not installed correctly.

Is one wire always hot on a 3-way switch? ›

Wiring for a 3-Way Switch

The most important wire to get right is the one connected to each switch's common screw terminal. This is the "hot" wire (usually colored black, but not always), and it brings the power from the source and delivers it to the first switch and then from the second switch to the light fixture.

How do you fix an unresponsive switch? ›

If your console has frozen and is unresponsive, press and hold the POWER Button for at least 12 seconds to turn the console completely off. Then press the POWER Button again to turn the console on. * A Nintendo Switch is pictured here. There are differences with the Nintendo Switch Lite.

What does a hard reset do to a switch? ›

Factory Resetting your Switch puts it in a re-sellable state and resets any software. A Hard Reset is used for issues that drastically affect your Switch, like issues that impede system navigation. Hard Resets can also restore your Switch to factory settings while retaining saved data for your games.

Why won't my switch wake up? ›

Hold down the POWER Button for twelve seconds to force the system to shut down, then power it on again. Reset the AC adapter by leaving it unplugged from both ends for at least 30 seconds. While performing this step, verify you are using the Nintendo Switch AC adapter (model No.

Why won t my electric switch stay up? ›

If your fuse switch won't stay on, it might be time to replace the blown capacitor you'll need to replace your fuse with a new one and then see if that solves the problem. You can find replacement fuses at the Electrical store near you.

How many years does a light switch last? ›

So, while light switches do wear out over time, there is no expected lifespan of a light switch, and a one-year-old switch can be just as likely to fail as a 20-year-old switch. Signs to look for: Popping or Cracking. Looseness.

Can a light switch go bad if wired wrong? ›

If a light switch is wired up wrongly, a short circuit may takes place if you give phase and neutral to the switch terminals. Always connect neutral wire to the one terminal of the light and phase to the one terminal of the switch and off wire to the other terminal of the switch to the light other terminal.

Why does my light flicker and then stop? ›

It could be a loose connection in just that circuit, or the circuit might be overloaded. If the lights are flickering throughout your house, you could have a more serious issue with all of the wiring. It could be an issue with the electrical panel or the main connections to your home.

Can light has power but won't turn on? ›

The Light Socket Has Power but the Bulb Won't Light

If your voltage or continuity test shows that the fixture is working but the bulb won't light, try another bulb. If that doesn't work, the problem is probably corroded terminals. To clean them, you need to unplug the lamp or turn off the switch and the breaker.

Why do LED lights randomly stop working? ›

Reasons often include a faulty power supply, loose connections, a faulty circuit design, or even damage due to water ingress caused by rain. Whatever the reason is for your LED lights not working and whatever the tell-tale signs are, there's usually a solution to the issue.

How do you tell if a light switch is bad with a multimeter? ›

Touch one probe of your multimeter onto each screw terminal on the light switch. Be sure to hold the leads firmly against the terminals and read the measured resistance on your multimeter. You should get a reading close to zero if the light switch is functioning correctly.

Can a faulty light switch cause a fire? ›

The main reason a light switch feels hot or shows signs of heat damage is from circuit overload. This happens when too much current flows through the switch. If the light switch is rated for 600 watts but 1,000 watts is flowing through it, the switch will get hot and possibly lead to a fire.

How often should you replace network switches? ›

WiFi Network: 2 to 3 years.

Wireless connections are getting faster than ever, and older WiFi networks can seem archaic, especially as networks expand. Furthermore, as you update software, you will want your WiFi network to be able to keep pace. Routers and Switches: 5 years.

How do you diagnose a switch? ›

Single-pole switch: Clip the wire of a continuity tester to one of the screw terminals, and touch the other terminal with the tester probe. Turn the switch lever on and off. The tester should light up when the switch lever is in the on position but should not light up when the switch lever is off.

How many hot wires does a 3-way switch have? ›

The two hot wires of the three-wire cable connect to a pair of brass-colored traveler terminals on each switch. The fixture's hot wire connects to the second switch's common terminal.

What is a dead end 3-way switch? ›

A dead-end switch refers to a wiring technique used to save wire when a lighting outlet is located between a source of supply and the switch location. Electrically the circuit is identical to a standard SPST switch circuit.

Do both switches have to be on for a 3-way switch? ›

Three-way switches are connected to a hot wire from the electric panel and a wire that connects to the light. However, they have two special wires that connect to each other, called travellers. These two wires create their own internal circuit so that if a light is off, either switch can turn it on.

What happens when a 3 way switch is wired wrong? ›

The light might not turn on, or might not turn off, or the circuit breaker might trip due to a short circuit, depending on how it is miswired.

What happens if you wire a 3 way switch backwards? ›

As earlier answers have said reversing the connections to L1 and L2 on one switch will result in your light being off when both switches are down. However it will also be off when both are up and the light will only illuminate when the switches are positioned differently.

Does a 3 way switch need to be grounded to work? ›

For safety, always install a three-way switch that has a grounding screw. It is connected directly to the metal strap of the switch, and it may be located on the bottom of the switch, as shown here, or it may be on the side or another location.

How do I completely reset my switch? ›

Complete These Steps:
  1. Select System Settings on the HOME Menu.
  2. Scroll down to System, and select it.
  3. Scroll all the way down to the bottom of the menu, and select Formatting Options. ...
  4. Select Initialize Console to delete all data in the system memory.

How do I master reset my switch? ›

Complete These Steps:
  1. Select “System Settings” from the HOME Menu.
  2. Scroll down to “System” and select it.
  3. Scroll all the way down to the bottom of the menu and select “Formatting Options”. ...
  4. Select “Restore Factory Settings” to delete all data in the system memory.

Why does my 3 way switch sometimes not work? ›

Sometimes, a 3-way circuit doesn't work because someone tried to replace a defective switch and did not properly connect the wires. Sometimes, one of the switches has become defective.

Why are there 2 red wires on light switch? ›

Red is “switched power”. One side should get a black wire (hot), the other side either a black wire (hot to the switched device) or a red wire (switched power).

Why does my light only turn on after many times turning on and off the switch? ›

Sounds like a dangerously defective light switch. Possibly something broken inside that may be arcing when the switch is in the Off position. You should get this checked - and soon - that's the exact kind of thing that could cause a house fire.

Does it matter where the hot wire goes on a switch? ›

Because the switch terminals are interchangeable, it doesn't matter which wire you put on each.

Does red wire go to white or black? ›

A simple standard electrical circuit has a black or red "hot" wire that carries power from the power source to the device (e.g., switch, fixture, outlet, appliance), a white neutral wire that carries the power back to the power source, and a green or bare copper ground wire that connects the device to the home's ...

Where do the white black and red wires go on a 3-way switch? ›

Three-way wire(which includes red, black and white wires) runs from the switch on the left to the switch on the right, with the white wire carrying ground and the red and black wires carrying the output from terminals in the left switch.

Which terminal does line voltage wire black go to on a 3-way switch? ›

The black (line) wire connects to the common terminal of the first 3-way switch. A 3-wire NM connects the traveler terminals of the first and second 3-way switch together. Traveler wires are interchangeable on each switch.

How do you tell which wire is hot when both are black? ›

Use a test lamp. It's just a light bulb with two wires coming out of the holder. Touch one lamp wire to one of the black wires and the other lamp wire to the ground wire. If the bulb lights up, the wire is hot.

Why won t my trip switch go back up? ›

If the breaker trips again you may have a short circuit or overloaded circuit, which will need to be checked out by a local licensed residential electrician. A circuit breaker that refuses to reset even after being turn to the 'off' position and back on may be broken and will need to be replaced.

Why does my 3 way switch keep tripping? ›

Newly wired switch tripping the breaker pretty much always means the switch is wired to short the supply. Triple-checking only works if you triple-check correctly - if you did it wrong once for some reason and triple-check it to be the way you did it wrong three times, it's still wrong.

Why does my switch keep getting tripped? ›

Reasons a safety switch may be tripping

A temporary electrical fault (these are easily fixed!) Rain damage caused by heavy falls (make sure you call an electrician for this one) Thunder, lightning and electrical storms can trigger RCD sensors (this usually resolves itself) Damaged wiring (worn out over time)

What is the three switch problem? ›

Open the door. If the light is on, then switch number 2 controls it. If the light is off, then go and feel the bulb with your hand. If the bulb is hot, then switch number 1 controls it, and if the bulb is cold, then switch number 3, the one you did not touch, controls it.

What position should a trip switch be in? ›

If a switch trips it will be in a downward position (opposite to the picture). In order to reset; first check that there is nothing obvious causing the circuit to trip e.g. water in a light fitting then flick the switch upwards and power will be restored.

Can a trip switch burn out? ›

Damaged wiring, fault or damaged appliances can cause ground fault. Circuit breaker trips or fuse burns out when a ground fault occurs to save us from harm.

How do I know if my switch is damaged? ›

Some signs of a bad light switch are clear. For instance, if there is an audible snap, crackle, or pop when you flip the switch, it's pretty obvious the switch is defective and it's time to replace it with a new one.

What is the common wire on a 3 way switch? ›

Black wire: This is a hot wire that carries electricity from the power source to the first switch in a typical 3-way setup. It's also called the “common wire” or the “line wire.” Unless the breaker is off, this black wire is always hot.

Where does the red wire go on a 3 way switch? ›

The black hot wire connects to the far right switch's common terminal. Red and blue wires link the traveler terminals of both switches. The red wire, which is connected to the first switch's common terminal, leads back to the fixture.

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