3 Way Toggle Switch Wiring. The black line wire connects to the common terminal of the first 3 way switch. In the 1st diagram below a 2 wire nm cable supplies power from the panel to the first switch box.
The key to wiring 3 way switches the power feed and the switch leg leading to the fixture s typically one at each switch location are attached to the screw terminal found at one end of the switch by itself. Touch the probes to the 3 wires removed from the switch until you get a reading on the tester indicating continuity. Converting a single pole switch to a 3 way 1.
This terminal is usually identified by a darker colored screw.
Do this before you disconnect any wires from the switches. Three way switches have 3 terminals to carry circuit electricity and one terminal for a ground wire. These are the runners of the circuit. Turn off the correct circuit at your electrical panel.
