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I want to test the switch and light socket for an outside light which stopped working. The switch and light socket (bayonet style) are similar to the ones in the photos below.

What's the best way to test them? I assume I would need to test the switch for continuity and then measure voltage across the light socket?

I have a non-contact voltage tester so would it be better (and safer) to use that instead for the light socket?

I also have a question regarding the voltage tester which has high and low sensitivity settings: before turning off power at the switchboard, with the voltage tester set to high, I get a voltage warning as expected. After turning off the power, the voltage tester is not activated but if I actually touch the tip of the voltage tester to one of the switch terminals I get a warning. The same thing happens when the voltage tester is set to low sensitivity mode and I make contact with one of the terminals.

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You've already experienced the flaws with non contact voltage testers.... they are not accurate. Get a good multi meter from your home store.

Make sure you check for any GFCI's outlets that might be feeding the light. They might have tripped.

Start testing from the socket and work your way toward the source. Look for your voltage between the switched hot and neutral with the switch on. If no voltage, test the switch load to neutral and hot to neutral. If no neutral, then test to ground. If neither, turn off power and check switch for continuity.The best way to do this is to disconnect the switch from the circuit after turning off the power and taking pictures of the original wiring. Then hook your leads from the multi meter to the screw terminals on the switch. With your meter set to "ohms", operate the switch. Your meter should go to zero ohms when the switch is on and go back to infinity ohms when turned off. If it doesn't do this then the switch is bad. If the switch is good and there's no voltage at the switch, then continue testing toward the main panel.

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  • could you go into a bit more detail about how to test the switch and the reasoning behind it?
    – jrcollins
    May 20 '21 at 0:25
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    @jrcollins Added additional testing to answer.
    – JACK
    May 20 '21 at 0:51
  • I understand what you said about testing the switch itself using the continuity function and testing the light socket for voltage between the hot and neutral. What I didn't understand was, "If no voltage, test the switch load to neutral and hot to neutral. If no neutral, then test to ground."
    – jrcollins
    May 20 '21 at 4:09
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    @jrcollins It could be the switch, the wiring or something beyond the switch toward the main panel.
    – JACK
    May 20 '21 at 11:50
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    @jrcollins "if no voltage" with a multi meter I was suggesting starting out at the socket with leads on the neutral and hot and operating the switch. If you got no voltage there, then go to the switch, leads on load screw and neutral, operate switch. If you now have voltage, then your wiring to the socket is bad and switch is good. If you don't get voltage, put leads on neutral and hot screw of switch. If you get voltage, then switch it bad. If you get no voltage then problem is beyond switch toward main panel..... Remember to check any GFCI outlets.
    – JACK
    May 20 '21 at 12:00
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Test that the light is good in a different socket

Poke the pins in the socket with a plastic rod, or an electrician's screwdriver, if they are both springy the socket is almost certainly good.

Turn the breaker off conform that it is off using your non-contact voltage detactor. This is what they are good for, it is pretty much all they are good for.

Now connect C and 1 on the switch. then turn the breaker back on, if the light glows now then the switch is bad, If it doesn't it's either the socket or the wiring that's bad.

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