Asked on May 28, 2023

My light switch won't work unless other switch is on, why?

Candice Cleaver
by Candice Cleaver

Hi everyone,

Got a bit of a weird electrical issue at my place. In one of my rooms, there are two light switches that control the same light. The problem is, one of the switches won't work unless the other switch is on. It's like they're playing a game of tag, and it's driving me crazy!

I've been doing some research and it seems like it could be a three-way switch problem or maybe a wiring issue. But I'm not an electrician, so I'm a bit out of my depth here.

Has anyone dealt with a similar light switch problem? What was the cause, and more importantly, how did you fix it? Can this be handled with a bit of DIY, or am I looking at getting a professional electrician involved?

Also, are there any safety precautions I should be aware of when dealing with electrical issues like this?

And one last thing - if I need to replace a switch or some wiring, any advice on what to look for when buying?

Any insights, advice, or experiences you guys can share would be a massive help.

Thanks in advance!

light switch won't work unless other switch is on

  12 answers
  • Could one of the switches be a master? If it is, that could be why. If not, I'd say call an electrician.

  • Cheryl A Cheryl A on May 28, 2023

    we have this in our home as well - a few of the light switches have to have both of them on for them to work

    I would call an electrician or go to local hardware store and see what they suggest

  • William William on May 28, 2023

    Sounds like they are three way switches and one has failed. You can replace the bad one with another three way switch or replace both if you can't tell which one is bad. Call an electrician if you don't want to work on them.

  • GrandmasHouseDIY GrandmasHouseDIY on May 30, 2023

    Yeah its a two way switch that has a "master" three way wire would be required to run back from one switch to another to create a true three way where both switches always have power so both switches work equally.

  • Kathy Gunter Law Kathy Gunter Law on May 30, 2023

    Often with a 3 way switch the circuit gets broken or there is short and they aren't "talking" to each other. Another possibility is the one that has to be on is the master. In either case, I would get a circuit tester to check and if that doesn't lend any light to the issue you can contact an electrician.

  • We have switches like this in our home, so you can turn the lights on and off from either entering or exiting the room. Sometimes you need to fix one or the other, but it's certainly not a DIY job. I'd call the electrician for sure.

  • Janice Janice on May 31, 2023

    If you have a master switch, you can turn it on and mark it with tape as a reminder not to switch it off so the other switch will always be on and will be able to turn the light on and off from the other switch.

  • Redcatcec Redcatcec on Jun 01, 2023

    You can figure out which is the master switch and leave it on, use the others to turn it on and off.

  • Deb K Deb K on Jun 01, 2023

    Hi Candice, hope this helps. It sounds like you have a three-way switch configuration, where both switches control the same light. In this setup, one switch is the "master" switch and the other is the "auxiliary" switch. The auxiliary switch only works when the master switch is on because it is designed to act as a remote control for the master switch. When the auxiliary switch is flipped, it sends a signal to the master switch to turn the light on or off. If the master switch is off, the auxiliary switch has no power to control the light.

  • Ah that's frustrating! Honestly, your best bet is to call a licensed electrician as you could really hurt yourself or burn your house down if you mess up the wiring. 3 way switches are a trickier kind of wiring so it's best left to a pro.

  • Mogie Mogie on Jun 01, 2023

    Hope this helps.

    To correct it, it would be best if you could disconnect both switches, and use a volt meter to find the constantly hot wire. Only one of the switches will have a constantly hot wire connected to it. Once you identify this wire, cap it with a wire nut and push it off to the side. The other 2 wires that were connected to teh switch will be the travellers. The travellers are the wires that run between the 2 switches.

    Connect the travellers to the 2 screws on the 3 way switch that are the same color. Connect the constantly hot wire to the screw that is marked "Common" on the back of the switch.

    At the second switch, the travellers should be the same colors that they are at the first switch. Connect them to the 2 screws that are the same color, and the third wire will connect to the odd colored terminal on the switch that is marked "Common" on the back of the switch. The common wire at the second switch is the wire that goes up to the light fixture. Typically, the 2 travellers come from the same outer jacket. That may help you identify the travellers.

  • Candice Cleaver Candice Cleaver on Jun 04, 2023

    Thank you everyone for all the great advice