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How to Troubleshoot Three-Way Switches

Toggling 3-way Switches

Test a 3-way Switch

  1. Turn off power to the switches at the circuit breaker and using a tester, make sure power is off. Remove the two 3-way switches so you can access the switch terminals. The wire connections do not have to be removed.
  2. Using a continuity tester, check continuity between the common (black) terminal and each of the traveler terminals (brass colored) of each 3-way switch.
  3. There should be continuity between the common terminal and only one of the traveler terminals. After toggling the switch, there should be continuity between the common terminal and only the other traveler terminal.

When a 3-way switch fails, there will usually be no continuity between the common terminal and one (sometimes both) traveler terminals of one of the 3-way switches.

3 Way Switch Up Position

Place leads of continuity tester on the common (black) terminal and one of the traveler (brass or silver) terminals

3-way Switch Down Position

Place leads of continuity tester on the common terminal and the other traveler terminal

120 V

Neutral

120 V

Toggling 3-way Switches

Locate a Bad 3-way Switch

Usually when a 3-way switch fails, lights can be toggled on and off at one switch, but not the other. If one of the two 3-way switches toggles the light(s) on and off, the other 3-way switch has probably failed. Follow these steps to find which switch is bad.

  1. Toggle each switch until the light come on. Toggle one switch to see if it turns the light on and off. If it does, it is a good switch. Leave the light on.
  2. Toggle the other switch to see if it turns the light on and off. If it does, it is a good switch and the other is bad.

One of these switches will not turn the light on and off (while the light is on) and that is the bad switch.

Once you identify the bad switch, follow the steps below to verify it is bad and needs to be replaced.

How to Test and Replace a 3-way Switch Video

Switches are spring loaded to minimize arching and prolong their life. However, a very small amount of arcing is present when a switch is toggled. A bad switch may not fail completely, burned contacts may cause intermittent failure. Keep this in mind when troubleshooting switches. Intermittent failure could make troubleshooting difficult, especially with 3 and 4-way switches. If one 3-way switch needs to be replaced, the other one should be replaced too.

Neutral

Electrical Troubleshoot ing

Meters and Testers

Battery Testers

Input Impedance

High Wattage Appliances

Circuit Breakers

Troubleshoot Outlets

Troubleshoot GFCIs

Troubleshoot Lights

Troubleshoot Switches

Troubleshoot 3-way Switches

Troubleshoot 4-way Switches

Open Neutral

Open Neutral Multi-wire Circuit

No Power to Outlets

Troubleshoot Garage Door Opener

How to Test and Replace a 3-way Switch Video