# Electricians: Help Me Troubleshoot Two 3-Way Switches **URL:** \ **Category:** Factual Questions\ **Created:** [June 24, 2014, 1:35am UTC](https://boards.straightdope.com/t/electricians-help-me-troubleshoot-two-3-way-switches/691502 "2014-06-24T01:35:42Z")\ **Posts on this page:** 12\ **Page:** 1
**Author:** ![BobArrgh](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/bobarrgh/32/2881_2.png) [@BobArrgh](https://boards.straightdope.com/u/BobArrgh)\ **Post date:** [June 24, 2014, 1:35am UTC](https://boards.straightdope.com/t/electricians-help-me-troubleshoot-two-3-way-switches/691502/1 "2014-06-24T01:35:42Z")
I have a question for you electricians. I have a hall light that has two 3-way switches. The light has been working for at least 20 years. About 7 years ago, I changed out the light fixture and replaced it with a fixture that had 3 halogen bulbs in it. The light and both switches have worked fine for the past 7 years. When I say “worked fine”, I mean, you could turn the light on or off at either switch without having to flip the other one. Turn it on upstairs, turn it off downstairs, and _vice-versa_. About 2 weeks ago, we started having problems with that light fixture in that the switches stopped working. I took both switches out of the wall, but left the wires connected, at first. From what I could tell, all the wires were seated correctly. (Please note: All electrical work discussed below was done with the circuit breaker off.) I started by replacing the downstairs switch because it looked like it had evidence of burning or a short. At the time, I did not realize that I had to make a note of the “common” black wire. However, I took a picture with my phone, and it looks like the other black wire and the red wire were twisted together. I replaced the switch with a new 3-way switch and put the single black wire into the common post and the other black wire and red wires onto the other posts. I pushed both light switches back into the wall and tightened them down. I tried the light but it didn’t work, and when I flipped the switch upstairs, the lights flickered on and then off again. My thought was that the upstairs switch probably had a loose connection that got exacerbated when I shoved the switch back into the wall. (All wires were inserted into the pressure clips, as opposed to being screwed down.) I then replaced the upstairs switch with a new 3-way switch. Now, however, I can only turn on the light when the upstairs switch is in one position and the downstairs switch is in the other. So, here are my questions: 1. My thought is that I may not have put the true common black wire on the common post on one of the switches. Is it OK to open one of the switches and change the black wire? 2. If that doesn’t work, what is my next troubleshooting step? Take out the light fixture and see if those wires are loose? 3. Is there an easy way to determine which wire in one switch is the same wire in the other switch? I have a multimeter but it doesn’t have a continuity checker. I tried to hook a battery up to check the continuity by testing DC volts, but couldn’t get a real good feeling I was doing the right thing. I’m afraid I just can picture the way the wires are connected in the wall. Any words of wisdom? Disclaimer: You are not my electrician. I am performing all work on my own house at my own risk. I make sure that the circuit breaker is turned off before doing anything with the light fixture or the switches. If I electrocute myself, it is my fault, not yours. Thanks. ---
**Author:** ![Magiver](https://avatars.discourse-cdn.com/v4/letter/m/4491bb/32.png) [@Magiver](https://boards.straightdope.com/u/Magiver)\ **Post date:** [June 24, 2014, 2:12am UTC](https://boards.straightdope.com/t/electricians-help-me-troubleshoot-two-3-way-switches/691502/2 "2014-06-24T02:12:37Z")
not an electrician but there is a [number of ways](http://www.homeimprovementweb.com/information/how-to/three-way-switch.htm) to wire a 3 way switch. ---
**Author:** ![Magiver](https://avatars.discourse-cdn.com/v4/letter/m/4491bb/32.png) [@Magiver](https://boards.straightdope.com/u/Magiver)\ **Post date:** [June 24, 2014, 2:19am UTC](https://boards.straightdope.com/t/electricians-help-me-troubleshoot-two-3-way-switches/691502/3 "2014-06-24T02:19:18Z")
I would think the first thing to establish is where power is brought in. ---
**Author:** ![aceplace57](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/aceplace57/32/3500_2.png) [@aceplace57](https://boards.straightdope.com/u/aceplace57)\ **Post date:** [June 24, 2014, 3:25am UTC](https://boards.straightdope.com/t/electricians-help-me-troubleshoot-two-3-way-switches/691502/4 "2014-06-24T03:25:55Z")
Is the OP sure the light fixture and bulbs are ok? The earlier problem may have burned them out. You’ll need a [meter](http://www.radioshack.com/product/index.jsp?productId=4214667) to check voltages. The earlier link has the various ways these circuits can be wired. You need to figure out which one is used in your house. Voltage checks can identify where the power comes from. Continuity checks can trace common connections. Always shut off power before attempting continuity checks. Experienced electricians use a meter for continuity checks. A easier way is a continuity checker. if it lights open then you have continuity. [http://www.walmart.com/ip/GE-Light-Up-Continuity-Tester/16561530](http://www.walmart.com/ip/GE-Light-Up-Continuity-Tester/16561530) ---
**Author:** ![aceplace57](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/aceplace57/32/3500_2.png) [@aceplace57](https://boards.straightdope.com/u/aceplace57)\ **Post date:** [June 24, 2014, 3:35am UTC](https://boards.straightdope.com/t/electricians-help-me-troubleshoot-two-3-way-switches/691502/5 "2014-06-24T03:35:48Z")
Sorry, I had a typo. if the continuity checker _lights up,_ then you’ve found two common wires. I prefer continuity checkers because they are quicker to use. It takes longer to read a meter. A meter is bigger/heavier to hold. I keep my continuity checker in my back pocket climbing ladders or up in the attic. DIYers need to be very careful with meters. You have to check for voltage using live circuits. Make certain the meter is set for AC. You’ll burn out the meter if it is set on the resistance range. ---
**Author:** ![aceplace57](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/aceplace57/32/3500_2.png) [@aceplace57](https://boards.straightdope.com/u/aceplace57)\ **Post date:** [June 24, 2014, 3:58am UTC](https://boards.straightdope.com/t/electricians-help-me-troubleshoot-two-3-way-switches/691502/6 "2014-06-24T03:58:20Z")
I have a non contact voltage checker too. Quite useful to quickly find a hot wire. [http://www.all-spec.com/products/NCVT-1.html?gclid=CJOtypTOkb8CFTSVMgodNzMAWg](http://www.all-spec.com/products/NCVT-1.html?gclid=CJOtypTOkb8CFTSVMgodNzMAWg) instructions/demo [![](https://img.youtube.com/vi/6F_wuU47PLU/hqdefault.jpg "Non Contact Voltage Tester") ](https://www.youtube.com/watch?v=6F_wuU47PLU) another simple tester. [![](https://img.youtube.com/vi/D_eb37WApx8/maxresdefault.jpg "Neon Tester -One Prong in your Hand") ](https://www.youtube.com/watch?v=D_eb37WApx8) ---
**Author:** ![bob\_2](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/bob_2/32/3341_2.png) [@bob\_2](https://boards.straightdope.com/u/bob_2)\ **Post date:** [June 24, 2014, 8:49am UTC](https://boards.straightdope.com/t/electricians-help-me-troubleshoot-two-3-way-switches/691502/7 "2014-06-24T08:49:00Z")
Here is another link with some drawings. > **[Wiring a 3-Way Switch](https://www.how-to-wire-it.com/wiring-a-3-way-switch.html)** > > How to wire a 3 way switch, How To Wire A 3-Way Switch Circuit and Teach You How The Circuit Works. ---
**Author:** ![BobArrgh](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/bobarrgh/32/2881_2.png) [@BobArrgh](https://boards.straightdope.com/u/BobArrgh)\ **Post date:** [June 24, 2014, 12:15pm UTC](https://boards.straightdope.com/t/electricians-help-me-troubleshoot-two-3-way-switches/691502/8 "2014-06-24T12:15:51Z")
Thanks for the help, all. I’ll give the suggestions a try. I know the light bulbs still work because the light fixture will come on in one configuration of switch settings. Tonight I will remove the light fixture and make sure all the connections are good and solid. ---
**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:** [June 24, 2014, 1:35pm UTC](https://boards.straightdope.com/t/electricians-help-me-troubleshoot-two-3-way-switches/691502/9 "2014-06-24T13:35:37Z")
> [@](#): > > I then replaced the upstairs switch with a new 3-way switch. Now, however, I can only turn on the light when the upstairs switch is in one position and the downstairs switch is in the other. Sounds like you got your wires confused. Identify the feed wire from the panel. Connect it to the proper terminal on one switch. Identify the load wire going to the light fixture and connect it to the proper terminal on the other switch. That leaves the two traveler wires. Connect them to the other two screws on both switches. If there is still a switching problem, reverse the traveler wires on one of the switches. Should fix it. ---
**Author:** ![BobArrgh](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/bobarrgh/32/2881_2.png) [@BobArrgh](https://boards.straightdope.com/u/BobArrgh)\ **Post date:** [June 29, 2014, 11:59am UTC](https://boards.straightdope.com/t/electricians-help-me-troubleshoot-two-3-way-switches/691502/10 "2014-06-29T11:59:54Z")
I found the problem: when I replaced the first switch, the common wire broke off at the terminal when I was shoving the switch back into the receptacle. Once I reattached it to the post, the light started working. Thanks to all for the suggestions. ---
**Author:** ![Tim\_T-Bonham.net](https://avatars.discourse-cdn.com/v4/letter/t/46a35a/32.png) [@Tim\_T-Bonham.net](https://boards.straightdope.com/u/Tim_T-Bonham.net)\ **Post date:** [June 30, 2014, 12:36am UTC](https://boards.straightdope.com/t/electricians-help-me-troubleshoot-two-3-way-switches/691502/11 "2014-06-30T00:36:56Z")
> [@BobArrgh](#): > > (All wires were inserted into the pressure clips, as opposed to being screwed down.) P.S. Not a good idea. Using the screw terminals on the side of the switches is more secure over the long term. ---
**Author:** ![BobArrgh](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/bobarrgh/32/2881_2.png) [@BobArrgh](https://boards.straightdope.com/u/BobArrgh)\ **Post date:** [June 30, 2014, 2:35am UTC](https://boards.straightdope.com/t/electricians-help-me-troubleshoot-two-3-way-switches/691502/12 "2014-06-30T02:35:13Z")
**t-bonham** , I should have said, “All wires **had been originally** inserted into the pressure clips …”. When I replaced the switches, I screwed the wires onto the posts. Thanks again, all!