# changing a light fixture without shutting off the breaker



## swimmer_spe

I need to change an outside light fixture. The problem is, I am unsure which breaker shuts it off, and there is no way of me knowing for sure.

What happens if I were to try to do it and just shut the switch off, what risks do I have of getting electrocuted?


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## Snoonyb

The switch should control the power to the fixture, which you can check with a VOM.


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## swimmer_spe

Snoonyb said:


> The switch should control the power to the fixture, which you can check with a VOM.



So, once I shut the switch off, there is no chance of being electrocuted?


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## Snoonyb

There is always a chance, however if it is properly wired the chances are remote, that's why I suggested the VOM.

Better safe than sorry.


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## swimmer_spe

Snoonyb said:


> There is always a chance, however if it is properly wired the chances are remote, that's why I suggested the VOM.
> 
> Better safe than sorry.



I have one, where should I put the 2 leads to?


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## jeffmattero76

With the switch off, put one lead on the white or bare ground wire (white is preferred), and the other lead on EACH of the black wires that are connected to the switch. Only one of them should show power. 

At the fixture, put your leads on the white and the black wires that were attached to the old fixture.

Far simpler to buy a non-contact voltage detector that beeps. At the fixture put the detector near each wire. If none of them beep, there is no power at the fixture box.


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## bud16415

Turn on the light and have someone watch the light as they call you on your cell phone. You turn off one breaker at a time until the light goes out. When they yell it went out mark that one as front light. I just did this the other day. If you don’t have a helper screw an adapter in where the light bulb goes and plug in a radio with your long extension cord and crank it up when the radio stops you know you have the breaker.


Doing the switch is ok as long as whoever wired it put the switch on the hot leg of the circuit. A switch will work fine turning a light on and off from the other leg some people call the common or neutral or the white wire. Power or hot should be the black wire.


The trouble with testing is in a lamp housing outside you will likely find wire nuts and tape joining the wires. You have to take them apart unless you have a non contact tester as mentioned above. If you are taking a wire nut off when it is hot be very careful as the wires might not be twisted and they will just fall apart when the nut is removed.


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## afjes_2016

The best and safest way to test is the way Bud suggested. 

Just shutting off the switch causing the light to go out does not mean that the conductors in the light fixture box are not hot. This would be the factor of a switch loop which means the power is coming from the light fixture box, going to the switch then the switch will allow power to go back up to the light to turn it on or off. If the light is wired this way just turning off the light will not necessarily mean there is no power in the light fixture box.

Simply buy something like this and screw it in to the fixture. Plug in a radio and turn it up high. Start flipping breakers until the radio shuts off. Again, as mentioned by Bud if you have someone to watch to see when the light turns off this is just as good. When the light goes off or radio shuts off the fixture box will be dead.

However there is a 1% chance that there may be more than one circuit in that light fixture box but very unlikely. That would happen more often in a junction box or multi gang light switch box.


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## swimmer_spe

bud16415 said:


> Turn on the light and have someone watch the light as they call you on your cell phone. You turn off one breaker at a time until the light goes out. When they yell it went out mark that one as front light. I just did this the other day. If you don’t have a helper screw an adapter in where the light bulb goes and plug in a radio with your long extension cord and crank it up when the radio stops you know you have the breaker.
> 
> 
> Doing the switch is ok as long as whoever wired it put the switch on the hot leg of the circuit. A switch will work fine turning a light on and off from the other leg some people call the common or neutral or the white wire. Power or hot should be the black wire.
> 
> 
> The trouble with testing is in a lamp housing outside you will likely find wire nuts and tape joining the wires. You have to take them apart unless you have a non contact tester as mentioned above. If you are taking a wire nut off when it is hot be very careful as the wires might not be twisted and they will just fall apart when the nut is removed.



The bulb is burnt out and for some reason, the bulbs keep blowing. That is why I am replacing the fixture.


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## Sparky617

Does the fixture vibrate when a nearby door is closed?  Have you tried an LED bulb?  If there is only one piece of Romex in the box the power feed comes from the switch box.  If there are multiple pieces of Romex in the box you may have a switch leg going to the switch and the power coming into the box for the light.


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## Michael Armstrong

Do the bulbs blow instantly or over a period of time?


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## Steve123

Just shut off the main breaker, shutting power to everything.


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## bud16415

swimmer_spe said:


> The bulb is burnt out and for some reason, the bulbs keep blowing. That is why I am replacing the fixture.


In the immortal words of Paul Harvey “And now we know the rest of the story.”


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## swimmer_spe

Sparky617 said:


> Does the fixture vibrate when a nearby door is closed?  Have you tried an LED bulb?  If there is only one piece of Romex in the box the power feed comes from the switch box.  If there are multiple pieces of Romex in the box you may have a switch leg going to the switch and the power coming into the box for the light.



No it does not vibrate. I tried a CFL and an LED. Lights for less than a second and then pops. What is Romex?



Michael Armstrong said:


> Do the bulbs blow instantly or over a period of time?





Steve123 said:


> Just shut off the main breaker, shutting power to everything.



I would rather not kill the power to the entire house.



bud16415 said:


> In the immortal words of Paul Harvey “And now we know the rest of the story.”



Yup....


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## Sparky617

Romex is non-metallic sheathed cable.  Standard 14/2, 14/3, 12/2, 12/3 cable.


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## Sparky617

If your bulbs are blowing immediately, I'd check the voltage from black to ground and black to white and from white to ground.  You should get 110VAC black to ground, black to white and 0 VAC from white to ground.


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## bud16415

Now that we know the rest of the story. There are only a couple things that will cause fast lamp failures like that. Most probable is corrosion in the socket. That will cause a high resistance that isn’t a problem as much as sparking at that point of high resistance. Think of turning the lamp on and off real fast.


I might try giving the socket a blast of fluid film. That’s a dielectric and cleaner then screw the lamp in and out a few times and see what happened. Keep in mind that’s what I might try.


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## swimmer_spe

Sparky617 said:


> If your bulbs are blowing immediately, I'd check the voltage from black to ground and black to white and from white to ground.  You should get 110VAC black to ground, black to white and 0 VAC from white to ground.



The fixture was working fine, then we noticed that the bulb burnt out. Then it would simply blow the new one instantly. So, to me, it sounds like something wrong with the fixture, and time for it to be replaced.


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## WyrTwister

Measure the voltage , as suggested .

     Just guessing by your narrative , very good chance you have a loose neutral ( " lost a neutral " ) some where with the wiring associated with that circuit .  

     No offense , again listening to your narrative , tracing that out probably is way beyond your skill set .

     Any other circuits in the house " acting up " ?  If so , the issue may be in your loadcenter or meter base or the power company's wiring coming into the house .

     Please report back .

Best of luck ,


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## swimmer_spe

OP here. Light fixture is changed out. 

I decided to do what one person suggested and trip the main breaker. Better safe than sorry.


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## oldognewtrick

swimmer_spe said:


> OP here. Light fixture is changed out.
> 
> I decided to do what one person suggested and trip the main breaker. Better safe than sorry.


So, I guess the bulbs aren't burning out like before?


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## swimmer_spe

oldognewtrick said:


> So, I guess the bulbs aren't burning out like before?



Nope.
I am guessing that water got into the fixture and caused corrosion that was causing the bulbs to blow.


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## Sparky617

swimmer_spe said:


> OP here. Light fixture is changed out.
> 
> I decided to do what one person suggested and trip the main breaker. Better safe than sorry.


Is it working fine now?


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## swimmer_spe

Sparky617 said:


> Is it working fine now?



Yup.


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