Sometimes the toughest thing to do is identify it. If there is no labeling on the switch, there may be a distinct color fastening screw used for the common terminal… may be black (for a newer switch) or “differently” colored than the 2 traveler terminals.
What’s the common terminal?
The common terminal is one among three electrically active terminals on a 3-way switch (not including the bottom terminal that is located on the metal frame of the mounting ears). The common terminal is the “bridge” between the power supply and the load (typically a light fixture). With this in mind, the wire that attaches to the common terminal is either (1) a hot wire from the main board or (2) leads to the load (fixture).
What are the travelers?
Travelers are two wires connecting the 2 3-way switches together. Referring to the graphic (above), the 2 traveler terminals on one 3-way switch are connected to the two traveler terminals on the opposite 3-way switch by the two traveler wires. Either traveler wire may be connected to either traveler terminal… it doesn’t matter!
Confused? Need an image?
X-Ray View of a typical 3-way circuit…
The above graphic courtesy Leviton Manufacturing Company
Replacing a defective 3-way switch…
(The graphic above will enable you understand the text below… and visa versa!)
NH’s rule for replacing defective 3-way switches is to ALWAYS REPLACE BOTH SWITCHES AT The same TIME! There’s a typical sense reason for this. If one switch has failed, how for much longer can the opposite one last? Besides, it’s a chore to find out which of the two switches has become defective. So in the long run it behooves you to spend just a few extra dollars now for a reward that can last for years or even decades!
Once you locate the common terminal, replacement of a defective switch is easy:
1) Attach the common wire to the common terminal on the new switch. The remaining two insulated wires are then attached to the remaining traveler terminals. Depending on the wiring in your house, the bare ground wire is attached to the ground terminal on the metal frame of the switch’s mounting ears. In case you wiring is up to modern codes, the common wire can be black and the travelers will be white
2) Screw the switches back into their boxes, put the switch plate covers on, and turn the ability on to check the switches. Amazing, is not it! You should now be able to show your light on and off from either switch.
What… it would not work? No luck? Well, you should not have connected the common wire to the common terminal! So now your assignment is to identify the common wire.
Identifying the common wires…
Sometimes, a 3-way circuit would not work because someone tried to replace a defective switch and didn’t properly connect the wires.
Sometimes, one of many switches has become defective.
The next method will address both problems without delay. The steps I’m going to describe might not be probably the most time-efficient option to troubleshoot a 3-way circuit. Laid out with y”all handyman-electricians in mind, it permits you to identify the common wires in both switch boxes with no possibility of error! You will want a multimeter to check voltage and continuity in the circuit.
1) Turn off the ability to the circuit at the principle panel. Disconnect all three wires (or four, if the outlet is grounded) from both switches. Separate the wires so that they’re as far away from each other as possible.
2) Turn the power back on. Now, using your multimeter, you are going to determine which of the three colored wires is the recent wire. There needs to be only one HOT wire in one in every of the 2 switch boxes. This is the common wire for that box. Set your multimeter to a minimum of 110 volts. Hold one of the probes on a known ground, comparable to a metal outlet box or a bare ground wire. Touch the other probe to the colored wires, one by one. The wire that registers voltage is the hot wire, and the common wire for this box.
NOTE: It is wise to also test the three colored wires in the other box for voltage also, if you have not already. There should not be any, but with the strange wiring I’ve seen through the years, it is worth taking a minute to do that. Using a voltage tester, touch one probe to a known ground (metal outlet box or bare ground wire) and the opposite probe to every wire. You should not get a voltage reading. In case you do find voltage, because of this this switch is meant to control another appliance, light, or outlet. Perhaps you’re checking the wrong switch?
ONLY One of many ELECTRICAL BOXES IN A three WAY CIRCUIT IS CONNECTED Directly to HOT TERMINAL OF The principle PANEL!!
After you have finished testing for HOT wires, turn the facility OFF! You won’t need power again until the switches are installed.
3) Install the primary 3-way switch within the box with the new wire, attaching the recent wire to the common terminal of the switch. Attach the other two wires, the travelers, to the other two terminals of the switch. If there is a bare ground wire, attach that to the ground lug of the switch.
4) Go to the opposite box (with no HOT wire). Set your multimeter to infinite resistance or to “continuity”. Touch one of many probes of the multimeter to a known ground, such as the metal outlet box or bare ground wire. Touch the opposite probe each of the three wires. Only one among them will register resistance or, when you’ve got a continuity tester, will cause a “beep”. You might have identified the common wire for this box.
5) As with the first box, connect the common wire to the common terminal on the new switch. Connect the opposite two wires to the TRAVELER terminals, and the bottom wire if applicable.
Screw the switches back into their boxes, put the switch plate covers on, and turn the power on to check the switches.
NOTE: In case your 3-way circuit uses an outlet or outlets instead of light fixtures, you might get confused with the wiring if the outlets are “split”… one of many plugs is always on and the opposite is controlled by the wall switch.
You can TELL IF THE OUTLETS ARE SPLIT BY LOOKING On the OUTLET. On the “hot” side, there’s a metal strip that connects the 2 screws. If this strip is broken, then the 2 plugs are independent of each other. There will likely be black (hot) wires attached to each screw terminal, though this alone doesn’t indicate that the outlet is split. It could mean that the outlet is connected to another outlet. IF THE METAL STRIP HAS BEEN BROKEN OFF, You can Make sure THE OUTLET IS SPLIT. IF NOT, IT Isn’t.
The primary two graphics show the metal strip or tab. The third and fourth graphics show how the tab is definitely removed with a set of needle-nose pliers. Once the tab is removed, the upper and lower outlet plugs are independent so one will be, for example, controlled by a wall switch while the opposite is always on.
If in case you have a split outlet, follow the identical 3-way switch troubleshooting as with a light fixture EXCEPT you’ll need to find out which outlet is always on.
After disconnecting all of the wires from the switches and from the switched outlet(s), turn the power on and test the wiring at the outlet. The new wire leading from the three-way switch circuit will haven’t any power, since all power must travel through the switches.
If one of many black (hot) wires does have power, then that is the wire for the “always on” plug. Turn off the power and mark it so you do not confuse it with the three-way circuit wires. Enjoy!!