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Checking Light Fixture Wiring Connections


By Dave Rongey - Summary:

How to Fix Your Light Fixture and Dimmer Switch Wiring Problems: The Most Common Problems with Light Fixtures and Dimmer Switches and How to Fix Them.

Guide to Light Fixtures with a Dimmer Switch and How to Fix Them

Electrical Question: I am wiring three 12V 50W halogen pendant lights over my bar, I wired the original 3 work lights but only the first halogen light works.

Additional Comments: Thanks for Your Help!
Background: Cheryl, a Homeowner from Kansas City, Missouri.

Dave’s Reply:
Thanks for your electrical wiring question Cheryl.

How to Fix Your Light Fixture and Dimmer Switch Wiring Problems

Application: Light Fixture Wiring.
Skill Level: Beginner to Intermediate.
Tools Required: Basic Hand Tools and Safe Ladder.
Estimated Time: Depends on personal experience, the light fixture and access to the light fixture.
Precaution: Identify the light fixture circuit, turn it OFF and Tag it with a Note before working with the wiring.
Notice: Replacement parts for the light fixture should be compatible with the type of lamps that have been installed.

Common Problems with Light Fixtures and Dimmer Switches and How to Fix Them

More about Light Switch and Fixture Wiring

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Wiring a Dimmer Switch
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Using Electrical Testers
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MORE ABOUT THIS TOPIC: Electrical Troubleshooting, Lighting, Pendant





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FAQs Frequently Asked Questions and Comments

22 Responses to “Checking Light Fixture Wiring Connections”
  1. Brian says:

    I have a room with 4 recessed ceiling fixtures. Most times when turning the switch on, 3 of the 4 lamps turn on. Sometimes, but not always, the 4th lamp will turn on after a minute or two. If you turn the switch off then back on, all 4 lamps turn on – this always occurs. The switch has been replaced, with no change noted. Any thoughts? Thanks, Brian R.

  2. Dave Rongey says:

    Hi John,
    If the wiring has not been changed then I would suspect the problem to be with the lamps or the ballast. Keep in mind that most fluorescent lamps last on an average of two years, depending on the number of hours of operation. If the lamps have been allowed to burn out in the socket, then the ballast may be bad as well. I would begin by installing a new set of lamps, and then see if they light up. If not then the connected ballast may require replacement.
    I hope this helps,
    Dave

  3. John Frendt says:

    Hi Dave, Three of five fluorescent lights that are 4 years old have stopped working, they all worked previously. They all operate on the same switch, and the lights are arranged in in X pattern. The feed is from the switch to light one, light one to two, light one to three, four and five, with a four wire connection. Lights four and five still work. Can this be ballast interference? When I disconnect light three, the center light, lights four and five still are the only working lights.
    Thank you

  4. Dave Rongey says:

    Hi Don,
    With the light fixture turned off, check the center metal tab inside the light socket at the base to make sure it is clear of obstacles and well positioned to make contact with the center contact of the light bulb. If the light socket shows signs of damage or it is broken then it may need to be replaced.
    I hope this helps,
    Dave

  5. Don Meyers says:

    Two of six light sockets in a dining room chandelier fixture cause the bulb to go on and off, then stay off as the bulb is screwed in. Inside the fixture, on the bottom, is a cardboard circle with a hole in the middle. What is likely to the problem?

    Thank you.
    Don

  6. Dave Rongey says:

    Hi Natalie,
    The following are some tips that may help to get this circuit working:

    CAUTION: Electric Panel work and testing is best performed by an experienced electrician.

    Because this is a newer home it sounds like this might be an issue with one circuit, therefore it would be good to check the circuit breaker to make sure it is in fact supplying power at the screw terminal of the circuit breaker. If the exact circuit is unidentified or not labeled in the panel then testing the voltage at each 15amp and 20amp circuit breaker would be the only way to verify all are working. Many times a circuit breaker may look like it is on, when in fact it may be tripped off.
    The neutral wire of the identified circuit should be checked for a secure connection into the terminal strip inside the panel.

    Inside the Home:
    Inspect anything that may have been recently changed within the faulty circuit and devices.

    When troubleshooting a circuit problem it would be good to check the devices closest to the panel location which would be the logical route of wiring and circuit delivery.

    I hope this helps you, and let us know what you have discovered.
    Be Safe,
    Dave

  7. Natalie says:

    The lights and ceiling fans went out in my kitchen dining room and living room all at the same time. The house is only 2 years old. It is not a breaker issue everything else works outlets, etc. I took apart the main light in the kitchen that has the main wire box re-tightened the wires together and that still hasn’t helped. I don’t really want to take apart the ceiling fans but if it will fix it I will. It seems like their would be a simple solution but I haven’t found it yet.

  8. Dave Rongey says:

    Hi Eric,
    Lets make sure the basics have been covered, starting with making sure that the pull chain switch for the light fixture is in the ON position. It could be that the pull chain switch is faulty, which may be discovered by testing the switch for continuity.
    I hope this helps,
    Dave

  9. eric schweitzer says:

    All 4 lights on my ceiling fan failed at once. The bulbs are good and the fan works fine.
    Any suggestions?

  10. Dave Rongey says:

    Hi Hill,
    Hearing a slight hum or buzz sound from a dimmer switch may be due to the brand and type of dimmer switch that you have. Lutron dimmers or Leviton dimmers rarely emit a hum or buzzing sound.
    It would also be a good idea to make sure the dimmer switch has been properly sized for the total amount of lamp watts that is being controlled by the dimmer switch. The most common dimmer switch is rated at 600 watts, however larger watt capacity dimmer switches are available in sizes such as 800 watts up t0 1000 watts and more.
    Loose mounted light sockets should be corrected to avoid an electrical short which can typically cause an electronic dimmer to stop working and need to be replaced.
    I hope this helps,
    Dave

  11. Hill says:

    We have a dimmer switch that buzzes faintly when we turn it on. We tried changing it out to a new switch but the buzzed too. The lights that it is controlling don’t make noise but one of the four does seem to be loosely mounted and flickers off occasionally. The light can’t be well visualized because they are behind a built in ceiling beam that can’t be removed. I am skeptical that the problem is with the connection at the light but I can’t figure out why the buzzing would go on at the switch. Any thoughts?
    Thanks so much.

    Hill

  12. Dave Rongey says:

    Hi Robert,
    The problem is most likely not the switch, otherwise the lamps would all be on off, but lets consider some other factors that may cause the lamps in the outdoor light fixtures to go bad:
    Are the light fixtures dusk to dawn or motion detector activated? If so then the light bulbs must be fully compatible, which includes incandescent and quartz lamps that are the specified type and watt size. Keep in mind that some CFL lamps do not work well with dusk to dawn fixtures or motion detector fixtures. For best results, make sure to review the light bulb requirements stated in the light fixture documentation.
    I hope this helps,
    Dave

  13. Robert Dauwer says:

    Hi, I recently replaced 3 outdoor lights for my mother. After about 2 weeks 2 of the bulbs died. I replaced them about a month ago all seemed fine again. now 1 month later all 3 are dead. All of the lights are on 1 circuit. Could the problem be the switch?
    Thanks for any suggestions.
    Robert

  14. Adam says:

    I ordered a light fixture off ebay and its not CSA approved for Canada standards. It requires 12v lightbulbs. If I just change transformer to equal rated CSA transformer is it ok to use rest of light fixture since its only 12volt and from what I gather doesn’t apply to code.

  15. Dave Rongey says:

    Hi Snap,
    When I hear about electrical wiring that is the old cloth type that is coming apart then yes, I always recommend replacing the wiring, especially if you like the house and would like it to be around for a few more years. As for troubleshooting the light fixture wiring, my process would be to identify all of the wires with the help of an externally grounded wire which will allow me to get a true reading about what is a power leg and what is not, otherwise it is easy to obtain false readings because a neutral wire can have 120 volts present as well as a power leg. It would also be good to identify the switch wiring which is best performed by turning off the power and using an Ohm meter. A key essential factor is to identify where the power source actually enters into the wiring. As all of these components of the circuit wiring are identified then the connections become clear. Keep in mind that the ceiling wiring may travel to other devices as well, so they need to be identified and tested as well.
    I hope this helps you, and please consider having the home rewired.
    Dave

  16. Snap says:

    I have a problem with a room ceiling light wiring. It is knob and tube and I cannot see the color. The switch worked before I took the light fixture off and put drywall over the plaster ceiling. It appears there are two black wires (hot) tied together and two white wires tied together (neutral). There are two remaining single wires. I put a tester to them and there is no voltage coming in. I put in a new switch and it still does not work. There is voltage coming in, as I get 110 volts when I put the voltage tester to the two tied black (hot) and the two tied white (neutral). Since the two remaining individual wires have the cloth that is rotting off, is there a short inside the wire. What can I do. I hope the answer is not to put in new wiring from the switch to the light box, as this is 1903 row house that has plaster walls and ceiling and that would be a huge job. Any suggestions on troubleshooting.

  17. Dave Rongey says:

    Hi Nathalie,
    From what you have described about the light fixture, make sure the 50 watt halogen bulb is actually 12 volts and not 120 volts.
    Dave

  18. Nathalie Rocher says:

    Hi,
    I have a desk lamp with a halogen 12V, 50W bulb. The bulb burned out and I replace it with new one. Now, when I turn ON the switch, the bulb wire becomes a little bit red but not much else.
    Is the new bulb faulty? Or is it the lamp?
    Thanks

  19. Dave Rongey says:

    Bill,
    If the white wire in the switch box was connected to the light switch then it was not a neutral wire, but instead it is a white wire that is being used as a switched leg. If the white wire in the switch box was not connected to the switch then the white wire may not be connected to the neutral at the preceding junction box, which may be the light fixture. Keep in mind that the wiring in a light switch box can not be used to tap into and power an additional 120 volt device unless both the hot and neutral is in the switch box.
    In case anyone is wondering, NO – a ground wire should NEVER be tapped into and used as a neutral, as that would create a hazardous condition within the home electrical system.
    Dave

  20. bill shaw says:

    I ran a 2 wire cable (black and white wire) from an existing junction box to a switch box to be able to power a light fixture and dimmer switch. At the switch box I spliced the white wire from cable in to the white wire going to the light box.I then connected black power wire in directly to switch.Then I connected black wire from the cable to the light fixture to the other terminal of the switch.At the light fixture white to white black to black. When I turn power back on nothing happens light doesn’t go on or off.I checked and I have power to the switch and power at the fixture. What am I doing wrong?

  21. Dave Rongey says:

    Hi Nicholas,
    The in this example of low voltage lighting the transformers are part of each of the low voltage fixtures, and the problem was compatibility with the dimmer switch. There are however, low voltage lighting systems that must have a separate transformer installed in a location which is has the 120 volt source leading from the switch. The transformer must be sized for the watt load of the lights, and the same for the type and gauge wire that is used for the lights.
    When a dimmer switch is used it must be compatible with the transformer and lamps being used.
    The transformer may be purchased from Home Depot, Lowes’ or a electrical wholesale supplier, and WAC is one brand, others of the same kind should work fine as well.
    Dave

  22. Nicholas says:

    I have the same problem, where did you buy the transformers? TIA

    Nicholas