How can I determine the routing of electric wires in my new house to troubleshoot non-functioning lights connected to unknown switches?
Asked by Ryan Evans 
4 months ago
Last Updated: May 16, 2024
Hey, do you know how we can figure out the path of the electric wires in the walls? We just moved into this house and some of the lights aren’t working, and we’re not sure which switches control which lights.
The first step is to replace any burnt-out light bulbs. It’s common for houses that are up for sale to have lights that need to be replaced.
Not a big deal. Just take down the light fixture from the ceiling and use a voltmeter to check for power. Make sure the breakers are all on and try different switches in the area to test for voltage. If there’s no power, start pulling out switches and plugs nearby to troubleshoot. You’ll probably uncover a bad connection or an installation error in the process.
Yes, tracking the wires behind the walls can be complicated, expensive, and very difficult, but usually it’s just a matter of a dead bulb, switch, or outlet that needs to be diagnosed and mapped with a voltmeter. No need for all the complex methods.
New homes typically come with a one or two year warranty.
It may take some practice and be a bit confusing at first, but once you get the hang of it, it works really well.
It might be an unnecessary purchase. You could consider hiring an electrician to diagnose the issue for a similar cost. It’s usually not a major problem.
Possibly, maybe not. It all depends on the end user. The question was asked and answered without making assumptions. The cost of that machine could cover an electrician’s fee for 1-3 hours, excluding any additional charges. It might also take a few weeks to schedule one since it’s not an emergency situation.
I’d estimate around $300 to fix as an electrician, and it should only take me 2 hours to get it up and running
You likely have switches for outdoor lights, like by the front door or the backyard, as well as inside for the coach light by the garage. There are switches for ceiling fans with lights in rooms like the family room and bedrooms, and some switches control outlets, often just the top or bottom. The dishwasher is also connected to a switch, along with a switch for the attic light in the hallway. ‘t forget about the switch for the fireplace and the pendant lights in the kitchen that were never installed.
As a licensed electrician, I can tell you that unless you have x-ray vision or tear down the drywall, there’s no foolproof way to know for sure. If I were to come to your house to fix this issue, I would bring new bulbs and test them out while trying different switches to identify the problem.
How about trying out a tone generator/detector? You can find some for under $20 or others for over $200. I would recommend getting a few from your local hardware store or online, starting with the cheaper options first to see which one suits your needs best. You can always return the ones that don’t work.
Thanks everyone for sharing your answers!
Klein offers a thermal imager that is compatible with your phone for around $135. Check online videos for more information.
Replace the lightbulbs.
When checking for power, it’s a good idea to use a non-contact tester to confirm power to the switch. Some testers can detect current-carrying wires from a distance, so it’s best to adjust the sensitivity by removing the switch plate and positioning the tester close to the switch. Be cautious not to set it too high to avoid detecting wires in the wall behind the switch. If the switch’s purpose is unclear despite having power, try turning off circuit breakers to see if any power readings vanish, which may help determine its function. Faulty switches could also be a possibility. Are the switches that appear non-functional labeled On and Off? If not, they may be 3-way or 4-way switches. An incorrectly wired switch could allow the light to be controlled from only one location if it’s on at the other location.