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A Wiring Diagram depicting 3-Way Switches with the LINE and LOAD in Separate Electrical Boxes

Three-Way Switch Wiring Diagrams

Dear Mr. Electrician: I need to see some three-way switch wiring diagrams.  I have two switches that control one light in my kitchen.  I am not sure if they are 3-way switches or 2-way light switches.  I find that one switch has to stay in the up position at all times just so the other switch will turn on the light.  How do I diagnose and fix this? Answer: This page has a few three-way switch wiring diagrams.  One diagram is above, the rest are below.  Two-way electrical light switches and 3-way light switches are the same thing, they just have different names according to country.  I am guessing that one of your three-way switches broke down.  NOTE: Text links below go to applicable products on Amazon.com and EBay. Shut off the electrical power for the circuit at the circuit breaker box.  Due to multiple wires being hot in this particular type of switch wiring it can be a little tricky for an amateur to diagnose which 3-way switch failed.  I suggest that you change one switch.  If that doesn't fix it, then change the other one.  It's a good idea to replace both switches at the same time anyway as the other one could fail soon after.  Be very careful to identify the LINE and LOAD wires BEFORE you disconnect the switches.  I usually take one wire off the old switch and put it on the new switch then repeat with the other wires.  Do not remove all of the wires from the one three-way switch at once and then try and figure what each wire is.  First thing is to take notice of the color of the screw terminals on the old switch.  One screw terminal will have a different color and will be labeled "Common".  That screw will have either a LINE or a LOAD wire connected to it. Thank you to John S. for the above photo depicting the common terminals on three-way switches.   The common terminals are the ones with the different color used for LINE and LOAD.  The unlabeled brass terminal screws are for the travelers to get connected to. You cannot rely on a color coded schematic wiring diagram to figure out what each wire's function is in an existing 3-way switch installation.  The original installers used whatever materials and wiring methods were acceptable at the time of installation.  There are old existing 3-way electrical switch installations that do not follow acceptable industry practice or electrical code requirements.  That is why it is important to identify the function of the wires for 3-way electrical light switches.  Changing a 3-way switch to a WiFi smart switch can be tricky.  You will need a neutral conductor to power the smart switch.  You cannot use the grounding conductor instead of a neutral.  In addition some changes may need to be made at the other 3-way switch in the circuit. Most likely the LOAD and one traveler will need to be connected together while the other traveler is capped with a wirenut. ...