# Two switches, ONE light. How do I know which switch is bad? **URL:** \ **Category:** In My Humble Opinion\ **Created:** [January 12, 2023, 6:49pm UTC](https://boards.straightdope.com/t/two-switches-one-light-how-do-i-know-which-switch-is-bad/978124 "2023-01-12T18:49:50Z")\ **Posts on this page:** 5\ **Page:** 2
**Author:** ![Chefguy](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chefguy/32/138_2.png) [@Chefguy](https://boards.straightdope.com/u/Chefguy)\ **Post date:** [January 14, 2023, 4:15pm UTC](https://boards.straightdope.com/t/two-switches-one-light-how-do-i-know-which-switch-is-bad/978124/21 "2023-01-14T16:15:27Z")
Just to give the OP nightmares: perhaps there is an open splice on a traveler in a junction box somewhere between the switches. 😆 ---
**Author:** ![excavating\_for\_a\_mind](https://avatars.discourse-cdn.com/v4/letter/e/e8c25b/32.png) [@excavating\_for\_a\_mind](https://boards.straightdope.com/u/excavating_for_a_mind)\ **Post date:** [January 14, 2023, 4:21pm UTC](https://boards.straightdope.com/t/two-switches-one-light-how-do-i-know-which-switch-is-bad/978124/22 "2023-01-14T16:21:42Z")
> [@Crafter\_Man](#): > > > [@Alessan](#): > > > > Tape one of them down. Now you have a room with one functioning switch. Problem solved. > > So when switch A is down, switch B is able to control the light? And when switch A is up, the light is off no matter what? > > If so, then I suspect an open contact in switch A: > … Not to sound snarky, just to point out the obvious: With the same diagram, if switch B is down, switch A is able to control the light and if switch B is up, the light is off no matter what. This would lead one to suspect an open contact in switch B. ---
**Author:** ![LSLGuy](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/lslguy/32/5813_2.png) [@LSLGuy](https://boards.straightdope.com/u/LSLGuy)\ **Post date:** [January 14, 2023, 7:12pm UTC](https://boards.straightdope.com/t/two-switches-one-light-how-do-i-know-which-switch-is-bad/978124/23 "2023-01-14T19:12:32Z")
> [@Chefguy](#): > > Just to give the OP nightmares: perhaps there is an open splice on a traveler in a junction box somewhere between the switches. 😆 Or better yet, just loose inside the wall in a stud bay. Buying a used house from a DIY idjit is always a voyage of discoveries. Mostly bad discoveries. Here’s hoping it’s just a craptacular contractor-grade switch that’s run its course. ---
**Author:** ![Chefguy](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chefguy/32/138_2.png) [@Chefguy](https://boards.straightdope.com/u/Chefguy)\ **Post date:** [January 14, 2023, 10:06pm UTC](https://boards.straightdope.com/t/two-switches-one-light-how-do-i-know-which-switch-is-bad/978124/24 "2023-01-14T22:06:18Z")
> [@LSLGuy](#): > > Buying a used house from a DIY idjit is always a voyage of discoveries. Our kitchen was done by someone who really didn’t understand how to do tile. We had to replace the floor tile, but decided to just live with the granite countertop tiles after getting a ridiculous estimate on replacement. ---
**Author:** ![Lucas\_Jackson](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/lucas_jackson/32/303_2.png) [@Lucas\_Jackson](https://boards.straightdope.com/u/Lucas_Jackson)\ **Post date:** [January 16, 2023, 8:11pm UTC](https://boards.straightdope.com/t/two-switches-one-light-how-do-i-know-which-switch-is-bad/978124/25 "2023-01-16T20:11:23Z")
> [@excavating\_for\_a\_mind](#): > > Pick the most used switch. Replace it with a new one. If that doesn’t work, take the switch you removed and replace the other switch with it. Less work than trying to troubleshoot it. Every time I have messed with three-way switches, I get dumber. If the house is old enough that the switches are failing, replace both now so you don’t have this issue again in the near future. [Previous page](https://boards.straightdope.com/t/two-switches-one-light-how-do-i-know-which-switch-is-bad/978124.md?page=1)