I have a 3 wire source I want to connect it to a switch on/off and then make it 2 wire to the light
Is the 3rd wire bare or green? And the first response you received is from a automotive electrician DO NOT TAKE THAT ADVICE automotive wiring is backwards from AC residential wiring. You can e-mail me or one of the other sparky's on this site for help just click our profiles and read the answers to verify our qualifications. Then click contact.
A three wire source generally means hot (white or red), neutral (black) and ground (green). If that's the case, eliminate the ground wire. It's not as safe, but will let you hook up using the hot and nuetral wires.
You probably have a red, white, and black wires first check with a voltage tester the black and whiteor red and white wires to see if you have power between those 2 wire if you dont you cant use it to feed the switch it may have been a 3- way switch. If you have power take the white wire from the light and splice with the white in the three wire and the black from the light goes to one of the screws on the single pole switch and the black or red from the 3 wire goes to the other screw on the switch ,does not make a differnce which goes where and make sure grounds are spliced (bare copper or green wire) A BLACK WIRE IS NEVER A NEUTRAL AND YOU NEVER GET RID OF THE GROUND IF YOU DONT KNOW THE ANSWERS TO QUESTIONS DONT ANSWER THEM YOUR BAD ADVICE COULD KILL SOMEONE
If you have black red and white, it could be wired for a three way switch, best to call an electrician as this is too complicated to write the testing procedures. If the wires are black white green more than likely the green is ground. Simple test with power on black to white 110v, black to green 110v, white to green 0v. If this is the case, ground the switch using the green wire to the ground terminal on the switch, whites from the power source is connected to white going to light using a wire nut or other approved method, both blacks are connected to the two brass terminal screws on the switch, it does not matter which terminals you use, just make sure when you are installing the switch back into the work box that off is down. Good luck and if you are in any way unsure call a licensed electrician, they'll only charge a service fee plus materials for a job that small.
