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

Three Way & 2 Way Light Switch Wiring Diagrams 2019

Dear Mr. Electrician: 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: 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 the three-way switches broke down.  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.  I don't remove all of the wires from the one switch at once and then try and figure what each wire is.  Take notice of the color of the screw terminals.  One screw terminal will have a different color.  That screw terminal will have either a LINE or a LOAD wire connected to it. You cannot rely on a color coded schematic wiring diagram to figure out what each wire's function is in an existing installation.  The original installers used whatever materials and wiring methods were acceptable at the time of installation.  There are old existing two-way and 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 two-way and 3-way electrical light switches.  Components of 3-Way & 2-Way Switch Wiring All three-way switch and 2-way switch wiring installations have the same basic components: Wires consisting of a LINE, a LOAD, a neutral, a pair of travelers, and two 3-way switches.  If you are trying to troubleshoot a 3-way switch operation, then you will need to identify the function of each wire.  Do this before you disconnect any wires from the switches.  The LINE wire is usually the easiest to identify because it is hot at all times.  It should be terminated on a copper or black screw on one of the 3-way switches.  The other three-way switch will have the LOAD wire connected to the copper or black screw.  A voltage tester is good for testing the live wires with neutral and/or earth ground. It is possible to simply replace the switches without having to identify the function of each conductor.  In this case you would just remove one wire at a time and put it on the same terminal on the new switch.  Take note of the color of the screw...