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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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Light Switch Wiring Connections
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


Wiring a dimmer switch

For more information about Troubleshooting
Troubleshooting Electrical Wiring

The following may also be helpful for you:

Dave's Guide to Home Electrical Wiring:

» You Can Avoid Costly Mistakes! «

Here's How to Do It:
Wire It Right with the help of my Illustrated Wiring Book

Great for any Home Wiring Project.
  electrical wiring  

Complete Guide to Home Electrical Wiring

Perfect for Homeowners, Students,
Handyman, Handy Women, and Electricians
Wiring GFCI Outlets
Wiring Home Electric Circuits
120 Volt and 240 Volt Outlet Circuits
Wiring Light Switches
Wiring 3-Wire and 4-Wire Electric Range
Wiring 3-Wire and 4-Wire Dryer Cord and Dryer Outlet
How to Troubleshoot and Repair Electrical Wiring
Wiring Methods for Upgrading Electrical Wiring
NEC Codes for Home Electrical Wiring
....and much more.

Learn more about Home Electrical Wiring
with my Online Video Course:
Basic Home Electrical Wiring by Example

Be Careful and Be Safe - Never Work on Energized Circuits!
Consult your Local Building Department about Permits and Inspections for all Electric Wiring Projects.

Electrical Tips to Help You Wire it Right

The Safest Way to Test Electrical Devices and Identify Electric Wires!

The Non-Contact Electrical Tester
This is a testing tool that I have had in my personal electrical tool pouch for years, and is the first test tool I grab to help identify electrical wiring. It is a Non-contact tester that I use to easily Detect Voltage in Cables, Cords, Circuit Breakers, Lighting Fixtures, Switches, Outlets and Wires. Simply insert the end of the tester into an outlet, lamp socket, or hold the end of the tester against the wire you wish to test. Very handy and easy to use.

The Quickest Way to Check for Faulty Electrical Wiring!

The Plug-In Outlet Tester
This is the first tool I grab to troubleshoot a problem with outlet circuit wiring. This popular tester is also used by most inspectors to test for power and check the polarity of circuit wiring.
It detects probable improper wiring conditions in standard 110-125 VAC outlets Provides 6 probable wiring conditions that are quick and easy to read for ultimate efficiency Lights indicate if wiring is correct and indicator light chart is included Tests standard 3-wire outlets UL Listed Light indicates if wiring is incorrect Very handy and easy to use.

Strip Off Wire Insulation without Nicking and Damaging the Electric Wire!

The Wire Stripper and Wire Cutter
My absolute favorite wire stripping tool that I have had in my personal electrical tool pouch for years, and this is the tool I use to safely strip electrical wires.
This handy tool has multiple uses:
The wire gauges are shown on the side of the tool so you know which slot to use for stripping insulation.
The end of the tool can be used to grip and bend wire which is handy for attaching wire onto the screw terminals of switches and outlets..

The wire stripper will work on both solid and stranded wire. This tool is Very Handy and Easy to Use.

More articles about Light Switch Wiring and Home Electrical Wiring:
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FAQs Frequently Asked Questions and Comments

4 Responses to “Troubleshooting Light Switch Wiring”
  1. 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?

  2. 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,

  3. 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.

  4. 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,