Light Switch Not Working? Here Are 4 Common Problems and Fixes

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A light switch that does not work is not only a nuisance, but it could be a health hazard as well. Walking into a dark room may lead to an accident, and a faulty light switch could signal more serious electrical problems. Fortunately, you can deal with many light switch problems yourself as long as you have a healthy respect for electricity and take all of the necessary precautions. Here are some of the most common light switch problems and how to fix them.

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1. Lights Flicker or Don’t Turn On

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Single-pole switches — those that control one or more lights from a single switch — have two power terminals and one ground terminal. The ground terminal is usually green, and the power terminals are usually brass or silver. One power terminal is connected to the power source, and the other is connected to the light.

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The wires should have the insulation removed and formed into a small loop that is secured under the terminal screws. If the connection is loose, the lights may flicker when you flip the switch, or the light may not work at all. Loose connections can also be fire hazards.

Sometimes, flickering lights could mean you have a bad light switch. Switches contain a spring and metal contacts that can wear out over time.

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How to Fix Flickering Lights

  1. Turn off the power at the service panel (circuit breaker box) by switching off the breaker for the switch's circuit.
  2. Use a screwdriver to remove the switch cover plate. Use a voltage tester to make sure the power is off. Remove the screws that hold the switch in place. Pull the switch from the box.
  3. The wire loop around the screw terminals should be installed clockwise, as this provides the tightest connection. If any are loose, tighten them. If either of the two wires is disconnected from the switch, this would cause the light not to turn on; connect the loose wire to the screw terminal that has no wire.
  4. Inspect the switch for burn marks or other signs of damage. If you see any, replace the switch. Likewise, if you correct bad wiring connections on the old switch and the light does not come on, replace the switch.

To replace the light switch:

  1. Unscrew the terminal screws, including the ground screw, and disconnect the three wires.
  2. On the new light switch, attach the bare or green ground wire to the ground screw. Connect each of the other two wires to one of the power terminals; these are interchangeable so you can’t mix up the wiring. You can leave the rest of the wiring in the box as is.
  3. Mount the switch to the electrical box and install the cover plate. Then, turn on the breaker to the circuit and test the light.

2. 3-Way Switches Don’t Work

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Two three-way switches work together to control one or more lights from two different switch locations. Each switch can override the other so that you can turn on the light at one switch but turn off the same light at the other. You often see this arrangement on stairs, long hallways, or where there are two entrances to a room.

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Sometimes, the switches don't appear to be in sync with one another. For example, you may not be able to turn the light off at one switch if it was turned on at the other. This often happens if one of the switches is replaced and not wired correctly.

Unlike single-pole switches, three-way switches contain a ground screw and three other terminals. One terminal, usually colored black, is the common terminal. On one switch, the common is connected to wiring from the power source, such as the electrical panel. The common on the other switch is connected to the light.

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The other two terminals, either brass or silver, are called traveler terminals. Traveler wires run between the two switches and are connected to the traveler terminals. If there is a problem, in many cases, it is due to one of the traveler wires being connected to the common terminal.

How to Fix 3-Way Switches That Stopped Working

Fixing three-way switches isn't always easy, but you can check the wiring to troubleshoot a problem.

  1. Turn off the power to the circuit and remove the cover plates from both switches.
  2. Use a voltage tester to make sure the power is off.
  3. Unscrew the screws that hold the switches in place and pull the switches from the box. In a typical configuration, there will be two different cables in each switch box. The wire to the common terminal should come from one cable. The two traveler wires should come from the other cable. In other words, the travelers are paired in one cable, while the common comes from its own cable.

It’s easy for a novice to attach the wrong hot wire to the common terminal on one of the switches. You may be able to tell which wires are which by examining them closely. If you can, attach the wires to the correct terminals. If you are unsure, call a professional electrician.

3. Dimmer Buzzes or Is Hot

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A dimmer that makes a loud buzzing sound or is hot to the touch could signal that the dimmer is handling more of an electrical load than what it was designed for. This happens when the combined wattage of the bulbs operated by the dimmer exceeds the wattage it is designed to support, or there could be a serious wiring problem in the home's electrical system. But be aware that dimmers often make a slight humming noise and that they are usually warmer than standard wall switches.

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How to Fix a Buzzing or Hot Dimmer

Remove a couple of the light bulbs and see how it affects the noise or heat at the dimmer switch. If the problem goes away, replace the bulbs with those of lower wattage.

If the problem does not go away, the dimmer may be bad and need to be replaced. A dimmer that is still hot to the touch will require help from a licensed electrician because the problem may not be with the dimmer but with the wiring in the home’s electrical system.

4. Dimmer Doesn’t Dim

When operating a dimmer switch, if the lights drop out, meaning they turn off before reaching the bottom of the dimming range, or they pop on, meaning they reach total brightness before you want them to, or the lights just won't dim at all, your dimmer or light bulbs may have compatibility issues. If the dimmer and the bulb in the light fixture are not compatible, the dimmer will not work properly. This happens often when homeowners replace incandescent bulbs with LED bulbs in fixtures that are controlled by a dimmer, especially older dimmers. Keep in mind that not all LED bulbs are dimmable, and not all dimmers are compatible with LED bulbs.

How to Fix Dimmer Light That Won't Dim

Determine if your bulbs and dimmer are compatible. If you have LED bulbs installed, make sure they are dimmable. If they are, replace the LEDs with incandescent bulbs and test the dimmer. If the dimmer works with incandescent bulbs, then the dimmer and LEDs are not compatible. If you can't find an LED that works well with the dimmer, you may need to replace the dimmer with a newer LED-compatible switch.

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