12 awg for 20 amp circuits and 14 awg for 10 and 15 amp circuits. The old switch had 3 screws on it.

Light Switch With One Red And Two Black Wires Dont Think
I have 2 black wires and 1 white wire. However if you need to rewire a light switch or a plug socket you may occasionally come across two black wires. Black means hot white signifies neutral and green indicates ground. 2 light brass and 1 dark brass named common. Essentially you connect the white and bare wires directly to the light and switch the black wire hot through a switch. Knowing which wire does what and goes where is imperative not only in the correct configuration of an electrical system but also for your familys safety. I tried to figure out the path of power but i wasnt getting the readings i was expecting.
When i pulled out the existing switch i noticed i have 2 black wires and a white wire connected to the old switch. In the outlet box you will have a black white and bare ground wire. Youll have two cables in the switch box a live one with a black and white wire and the one going to the outlet which has a red black and white wire. All home electrical wires made in the us. Its essential that you determine which black wire is hot before proceeding. The ground is screwed into the box so i understand that.
Follow standard color codes that identify each wires function in a circuit. The easiest and safest way is to use a multimeter to test for current. They should both be of the same wire gauge.