Typical 3 way switch wiring nm cable in the 1st diagram below a 2 wire nm cable supplies power from the panel to the first switch box.
Three way light switch wiring.
The black line wire connects to the common terminal of the first 3 way switch.
Connect the ground wire to the green screw.
The two hot wires of three wire cable connect to a pair of brass colored traveler terminals on each switch.
So what you should see if you have correct 3 wire electrical cable romex is a black power white neutral and now a 3rd red wire.
Regardless of what 3 way switch wiring diagram you re following you ll need to use a 3 wire cable to connect the two 3 way light switches.
A 3 wire nm connects the traveler terminals of the first and second 3 way switch together.
Installing the switches and light 1 attach the black power cable from the wall to the general screw black in the three way light switch.
Connect the two remaining traveler wires to the two brass or light colored screws.
In this diagram the incoming hot wire attaches to the first switch s common dark colored terminal.
When wiring a 3 way switch first screw the terminal screws of the new switch until they are difficult to turn.