How to Fix a Hot or Buzzing Dimmer Switch

Man adjusting light dimmer

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Dimmer switches can sometimes become warm or make buzzing sounds. While these problems aren’t an immediate threat, they should be addressed promptly. Warm or buzzing dimmers may be caused by a number of factors. You can try one or more quick remedies to eliminate the problem, but often the best solution is to replace the old dimmer with a new dimmer switch that is properly rated for the lights it controls.

Warm Dimmer Switches

Dimmer switches interrupt the flow of alternating current (AC) moving through your circuit. These breaks in electricity are what give dimmers the ability to provide a variety of lighting levels. But over time, the electricity flowing through the dimmer builds up heat and needs to be dispersed. Many dimmer designs dump this heat into the metal cover plate of the switch as well as into the electrical box housing the switch. It is normal for cover plates to be slightly warm to the touch, but they should never be hot.

Note that dimmer safety/heat ratings only apply to switches in solo or single-gang electrical boxes. Several dimmers in the same multi-gang box can generate potentially unsafe levels of heat. Dimmers wired in a group should have a reduced maximum load of 100 watts per switch.

  • Buy a larger face plate: Increase the heat transference for a single dimmer by installing a larger face plate, preferable a metal one. A large metal plate transfers more heat than a small plastic plate, keeping the dimmer cooler.
  • Remove excess insulation: Insulation behind a dimmer traps heat in the box. To minimize this problem, shut off the power to the switch at the circuit breaker, then remove the switch's face plate. Look for any visible insulation around the switch box. Use a plastic putty knife to push any excess insulation away from the box. Do not use this solution for boxes in exterior walls, where insulation is important for reducing heat loss from the home.
  • Lower the bulb wattage: Higher-wattage bulbs draw more power through your dimmer and can contribute to a rise in temperature. This is especially true with multi-bulb fixtures.

Buzzing Dimmer Switches

The hyper-fast AC interruptions that change lighting levels can cause a buzzing sound under the right circumstances. In some cases, the interruptions produce vibrations in the electromagnetic field within the bulb or within the switch itself, resulting in a buzz. Overloading your dimmer with excess wattage can also result in buzzing and humming.

  • Change the bulbs: Buzzing coming from the fixture itself is usually related to bulb filaments. Longer filaments are more susceptible to electromagnetic changes, which can result in constant buzzing. Installing new bulbs with shorter filaments can solve this problem. Better yet, replace energy-wasting incandescent bulbs with dimmable LED bulbs. LEDs are far more energy efficient, and they don't use filaments.
  • Consider usage: Running high-wattage bulbs for low lighting can place extra stress on your dimmer and cause buzzing. Install lower-wattage bulbs if you keep your lights at a lower setting on a regular basis.

Tools and Supplies You Will Need

  • Screwdrivers
  • Non-contact voltage tester
  • Dimmer switch
  • Wire strippers
  • Light bulbs (as needed)

Instructions

Humming or buzzing coming from the dimmer itself may be a sign of an overload. All dimmers are rated to handle a maximum wattage. Running too much power through your dimmer may cause a buzzing sound. Removing several bulbs from your dimmer’s fixture is a simple way to troubleshoot a potential overload. If the buzzing stops after reducing its wattage, it’s time for an upgrade.

Turn Off the Power

Shut off the power to the lighting circuit by switching off the appropriate circuit breaker in your home's electrical service panel (breaker box).

Test for Power

Remove the screws on the dimmer's cover plate and remove the cover plate. Unscrew the mounting screws on the switch and carefully pull the switch out of the box without touching any wires. Test each wire connected to the switch with a non-contact voltage tester to confirm the power is off.

Remove the Old Dimmer

Unscrew the wire connector from each set of wires on the switch, and separate the wire pairs. Remove the switch.

Connect the New Dimmer

Strip 1/2 inch of insulation from each wire lead on the new dimmer, using wire strippers if the wire ends are not already stripped. Connect the ground lead to the circuit ground wire in the box, using a wire connector. Connect each "hot" wire lead on the switch to one of the hot circuit wires in the box, using wire connectors. If there are neutral wires in the box, they typically do not connect to the switch.

Mount the Dimmer

Tuck the wires into the box while pushing the switch into place. Secure the switch to the box with the provided screws. Install the switch cover plate.

Test the Dimmer

Restore power to the circuit by switching on the circuit breaker in the service panel. Confirm that the light bulbs in the fixture are compatible with the new dimmer, and replace any bulbs, as needed. Test the dimmer for proper operation.