How to Diagnose No AC Power at Electrical Switch


AC electrical switches are relatively simple mechanisms. You flip a switch and the switch allows electrical current to flow to the object wired to the switch. In most cases this a light switch. A light switch has a wire connected to it that goes to the service panel and it has a wire that goes to the light. Troubleshooting a bad light switch is relatively straightforward.

Things You'll Need

  • Screwdriver
  • Wire nut
  • Inspect the service panel, often called the breaker box, for a tripped breaker. Each breaker in your service panel has "on/off" printed on it. If the lever on the breaker used to connect the light switch to the electrical grid of your home is switched toward "off," flip the breaker back the "on" position and then check the light switch again. If none of the breakers were tripped, proceed to Step 2 in this article.

  • Turn off the breaker that runs the electrical switch. If you do not know which breaker it is, turn off the home's main breaker.

  • Remove the cover plate from the light switch and then remove the screws that secure the switch to the electrical box.

  • Check the screw terminals with an electrical tester to confirm no power is entering the switch. Electrical testers are not expensive and they offer peace of mind to ensure you do not receive an electrical shock.

  • Remove the screws that hold the two wires onto the switch terminals. Straighten both wires, twist the ends of the wires together and cap them with a wire cap.

  • Turn on the breaker. If the light comes on, the switch is bad. If the light does not come on, there is an issue with the light itself or the wiring.

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  • Photo Credit worn light switch - on image by Five Arrows from
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