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Troubleshooting Light Switch Wiring

I just changed a light switch and lost power to my outlets, what did I do wrong? How to Check Light Switch Wiring Connections, Common Light Switch Wiring Problem and Solution.

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Electrical Question: I just changed a light switch and lost power to my outlets, what did I do wrong?

I just replaced a chandelier in the Dining Room of our home and changed the wall switch to a single pole dimmer switch.

This Home Electrical wiring question came from: Joe, a Homeowner in Indiana.

Dave’s Reply:
Thanks for your home electrical question Joe.

How to Check Light Switch Wiring

wiring electrical switches

Application: Replacing Light Switches
Skill Level: Beginner to Intermediate. This electrical work is best performed by a Licensed Electrical Contractor.
Tools Required: Basic Electricians Pouch Hand Tools and Voltage Tester.
Estimated Time: Depends on personal level experience and ability to work with tools.
Precaution: Identify the light circuit, turn it OFF and  Tag it with a Note before working with the wiring.
Notice: Installing additional fixture wiring should be done according to local and national electrical codes with a permit and be inspected.
Materials: Make sure the replacement light switch has the same amperage and voltage rating as the original switch, and is fully compatible with the electrical circuit, the light fixture and the type of light bulbs being used.

Common Light Switch Wiring Problem and Solution

Example of a Switch Wiring Connection Where there is a Outlet on the Same Circuit:

More about Wiring Light Switches


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FAQs Frequently Asked Questions and Comments

4 Responses to “Troubleshooting Light Switch Wiring”
  1. Dave Rongey says:

    Hi Travis,
    If you are trying to get 120volt circuit power from a light switch box where there are only two wires be sure to understand that the two wires to a standard single switch is only a loop of the power wire of the circuit, and in this example the white wire is not a neutral wire, it’s just a wire used for switching the power line of the circuit. A 120 volt circuit power requires the power wire, the neutral wire, and the ground wire.
    When testing wires at a light switch it is important to note that the measurements will be affected by the continuity through the light bulb. It may be helpful to remove the lamps from the light fixture to get a true and accurate test reading.
    I hope this helps,

  2. Travis says:

    I have a light switch. When I turn it on I loose 120 power, then when turned off I get it back. I took the wire for the light off the switch and the 120 power is on the top and bottom.

  3. Dave Rongey says:

    Hi Robert,
    I would double check the wiring of the switch which was replaced in the beginning. Make sure the wiring is not connected in series, then double check all the circuit wiring connections. This sounds like a neutral feedback problem which occurs when there is a lost or loose connection. Verify and test the power source and how it travels to each switch and to each light. Make sure the neutral is not mixed up into the switching process and make sure the ground wires are bonded. As you verify the circuit it would be helpful to sketch the circuit for a visual understanding which will aid for further testing and troubleshooting.
    I hope this helps,

  4. Robert says:

    I changed a kitchen light switch and all worked fine. The switch is on the same breaker as the hall and outside light switch. The past couple months the kitchen light started to come on but at low light, and when one of the other switches either at the hall or outside switch was on the light worked fine and continued to work after additional switch was turned off. The last couple of weeks, the kitchen light started to blink when turned on. If one of the other switches was turned on, the kitchen light would turn off. The outside light and hall light was working but now do not come on at all. All the breakers and wiring has been checked and receive 120volt through all the wiring.
    When an energy saver bulb is used it blinks in all sockets, however a regular light bulb does not work at all.
    Any suggestions? What to check next?