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Mike G.
Mike G., Master Electrician
Category: Electrical
Satisfied Customers: 7346
Experience:  Proven Professional 48 years Experience
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I have a dead light fixture that is at the end of the

Customer Question

I have a dead light fixture that is at the end of the circuit. It is wired like this. http://imgur.com/jPYQUAk
I have been troubleshooting for the past few weeks and I cannot find the break or loose wire.
Any help or additional steps of troubleshooting would be much appreciated. I really don’t want to start breaking drywall and plaster if I don’t have too.
About 4 weeks ago the light in the room flickered for a day or two then stopped working. Thought it was the bulb. Swapped bulb, still no light.
Checked the light switch with a multimeter, light switch is functioning correctly.
Checked the voltage at the light switch and there was very little to none.
Pulled the fixture down and checked the continuity between the switch and the fixture and continuity is good. No breaks in those wires. See picture of wiring diagram.
Checked the incoming/source wires and there is no voltage coming into the fixture.
I pulled all the outlets out in the room to see if there was any loose wires. All outlets are working and all wires are tight. None of the outlets are using the back holes for wiring.
I attempted to use my tone generator to trace the wire but this proved worthless. The tone generator is loud everywhere I go within 1-2 rooms of the tone box. (Power was off when I did this)
I made an outlet continuity tester to see if I can find the source cable in any of the outlets near by. No luck….. (Power was off when I did this)
I checked all outlets within 1 room above and below this room/light switch and all of them are working, tightly connected with no issues.
All outlets and lights in the house are working no issues or flickering.
I am at a loss on this one. Help.
Also, I am in the US. The home was built in 1952. It is copper wiring with cloth/braided insulation. Room in question is in the older part of the house.
Submitted: 1 year ago.
Category: Electrical
Expert:  Mike G. replied 1 year ago.

Hi, I'm Mike G and I'll be glad to assist you. Do you have a 2 wire voltage tester? If so, did you test the terminations on the switch to ground?

Customer: replied 1 year ago.
no voltage or very low under 20 volts.
Expert:  Mike G. replied 1 year ago.

What colors are the wires on the switch?

Customer: replied 1 year ago.
White and black. Here is a wire diagram. https://i.imgur.com/jPYQUAk.jpg
Expert:  Mike G. replied 1 year ago.

That indicates the feed is in the ceiling box. Check the connections on the black and white connected together, that is the hot to the switch. If the voltage to ground is still low, you'll need to check ceiling openings in adjacent rooms, twords the panel. That is the likely way it was wired. Sometimes the heat from a fixture will cause a failure on a wire connection.

Customer: replied 1 year ago.
The room is on the first floor. The basement below is open, but the first floor is plaster ceilings and the second floor"floor" is tile. I have no openings other than light fixtures.
Expert:  Mike G. replied 1 year ago.

OK, check them for a bad connection. Flip the breaker off first to see what else is on the circuit, then you'll know which ones to check.

Customer: replied 1 year ago.
Checked all the first floor light fixtures. There are 3 of them. All of them are good.
Expert:  Mike G. replied 1 year ago.

If you checked their connections OK. If you just turned them on, that won't get it. Turn off the breaker to the dead light. See what else is off. Turn the breaker back on and check the closest fixtures to the dead light. Drop the fixture and check the black wire connections. Check while doing that to see if the dead lightcomes back on.

Expert:  Mike G. replied 1 year ago.

One more thing, did you test both screws on the switch for voltage. If you only did one for the 20V reading, check the other. It could be a bad switch.

Customer: replied 1 year ago.
I pulled the fixtures and wiggled the wires to see if anything flickers and if everything was tight and nuts were still secure.The issue with this old house is that even with all the breakers turned off, some lights stay on.
Customer: replied 1 year ago.
I checked the switch for operation and it is working correctly.The source power comes into the fixture then it is wired down to the switch. There is only two wires in the switch.
Customer: replied 1 year ago.
the source black wire coming into the dead fixture is 0 volts to ground.
Expert:  Mike G. replied 1 year ago.

The flipping the breakers was to find out which one causes the 20V reading to zero. That breaker off will show you what is on the circuit to be checked. It may be fixture openings or possibly a receptacle ahead on the circuit.

Customer: replied 1 year ago.
Only hitting the main breaker makes the 20v go to zero. all breakers off with the main on still shows 20v.
Expert:  Mike G. replied 1 year ago.

If it is as you say, you have a serious problem, not only with the one dead fixture. If the voltage is off the main breaker there is a potential for a fire. It may be best to bring in a good electrician as soon as possible. It would not be wise to continue here. Good luck, get someone now.

Customer: replied 1 year ago.
What i mean is that when all the breakers are off, there is power to some outlets. When i hit the main breaker off, then everything is off.
Expert:  Mike G. replied 1 year ago.

That says the general lighting circuit is much over fused and the failure of one light is only a warning of what could lead to a fire. Get an electrician.