Lights can usually be toggled on and off at one switch but not the other when a 3-way switch malfunctions. If one of the two 3-way switches turns on and off the light(s), the other 3-way switch has most likely failed. To troubleshoot a 3-way switch first you need to locate the bad switch, test it right away and fix or replace it following the proper steps.

3 Way Switch Troubleshooting
Three-way switches are frequently used to control a light fixture from two places. To reduce arching and extend the life of switches, they are spring-loaded. When a switch is toggled, however, a minor amount of arcing occurs. A faulty switch may not fail altogether; instead, burned contacts may result in intermittent failure.
When troubleshooting switches, keep this in mind. Intermittent failure, especially with 3 and 4-way switches, can make troubleshooting challenging. If one of the three-way switches needs to be replaced, the other should be done as well.
When to Troubleshoot
A three-way switch does not require constant troubleshooting. You don’t even have to do this regularly because this isn’t a piece of software that needs upgrading or troubleshooting. Your switches may, however, become malfunctioning at times.
When the switches aren’t working, you’ll most likely need to troubleshoot. Naturally, this assumes that your light bulb is in good working order. If it is, and the switches aren’t turning on or off the lights, you’ll need to troubleshoot. It’s also possible that only one of the switches is broken.
Another example is when the wires are not connected properly. A non-functioning switch can be caused by incorrect wiring, which you won’t know unless you’re an electrician.
Locate a Bad 3-Way Switch
Lights can usually be toggled on and off at one switch but not the other when a 3-way switch malfunctions. If one of the two 3-way switches turns on and off the light(s), the other 3-way switch has most likely failed. To determine which switch is first, toggle each light switch until it turns on.
Toggle one switch to see if it turns on and off the light. It’s a good switch if it does. Keep the light turned on. Check the other switch to see if it turns on and off the light. If it does, it’s a fine switch, otherwise, it’s a terrible one. Thus, the bad switch is the one that will not turn the light on and off when the light is turned on.
Test a 3-Way Switch
Here are the steps of testing a 3-way switch.
Step 1: Remove The Switch
Turn off the circuit breakers’ switches and use a tester to check sure the electricity is turned off. To gain access to the switch terminals, remove the two 3-way switches. It is not necessary to remove the wire connections.
Step 2: Check Continuity
Now turn on the switch. Check continuity between the common terminal and each of the 3-way switch’s traveler terminals with a continuity tester. The common terminal and only one of the passenger terminals should have continuity.
After toggling the switch, the common terminal and only the other passenger terminal should be coupled. When a 3-way switch fails, there is frequently no continuity between the common terminal and one or both of the 3-way switches’ traveler terminals.
Replacing a Defective Switch
When it comes to three-way switches, replacing the two switches at the same time is strongly advised. The reason for this is that because they were both put at the same time, one will most certainly fail soon. Here are the steps for replacing a defective switch.
Step 1: Follow the Steps of Testing a 3-Way Switch
You have to go through the testing process first. Remove the switch. Make sure you’ve turned it off. Then check the continuity as stated.
Step 2: Find a Live Wire
From the continuity test, you can find the live wire. Check each wire for ground. Since the ground wire is where the electricity flows, it is often referred to as a “hot” or “live” wire. There should only be one live wire in a three-way switch, which is the common wire.
There shouldn’t be another live wire on the other switch if you detected the live wire on one. Return to the circuit breaker to switch off the electricity once you’ve located the live wire.
Step 3: Install a New Switch
To the terminal with the live wire, install a new switch. The live wire should be connected to the common terminal. Connect the traveler wires to the other two terminals after that. With all the wires inside, close the new switch.
Step 4: Go to the Second Switch
Now go to the second switch and remove the old switch. By touching one of the continuity tester probes to the wires, you can find the common wire. In one of those wires, there should be a beep. The common wire is the one that beeps or registers a resistance.
Step 5: Complete the Connection
Connect the common wire to the common terminal in the same way you did with the first terminal. Connect the other traveler wires to their terminals after that. With all of the wires inside, mount the new switch on the wall.
Some Tips
Troubleshooting a three-way switch appears to be a difficult chore at first. It is preferable to consult a professional if you have no experience with electrical lines and are uncomfortable doing so. DIY may appear to be the most cost-effective option, but if you’re going to wire it or risk receiving an electrical shock, it’s not worth it.
Another suggestion is to make a notation on the wires. People are prone to overlooking this because spotting a live wire is not difficult. However, you should do this not only now, but also in the future when troubleshooting. Even if the other wires aren’t labeled, don’t forget to label the common wire. A simple piece of colored tape will suffice.
Conclusion
Many features of a 3-way switch differ significantly from those of a typical wall switch. As a result, it’s fairly uncommon for homeowners to encounter problems with 3-way switches. Hopefully, our tips and steps will make the 3-way switch troubleshooting more accessible.
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