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 in a timely manner. Here’s a quick look at the causes of warm or buzzing dimmers and how you can fix them.

Warm Dimmer Switches

The cause: 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 front of the switch.

Dimmer heat transference is usually undetectable when the switch is running 100 watts or less. Heat does become noticeable when the power load approaches 300 watts. All dimming wall switches are designed to dissipate one watt of heat for every 100 watts of controlled load. This means that even at a full circuit load, your dimmer will never exceed unsafe temperatures.

Dimmer safety ratings only apply to switches in solo or single-gang junctions. Several dimmers on the same circuit can generate potentially unsafe heating levels if wired incorrectly. Dimmers wired in a group should have a reduced maximum load of 100 watts per neighboring switch. Have a professional electrician inspect your dimmers if the switch plate becomes too warm.

The solution: Buying a larger face plate is a simple way to reduce heat transference. The larger the plate, the more heat it can absorb before reaching a dangerous temperature. The material of your electrical box can also affect the heat transfer of your dimmer box. Plastic boxes are less conductive than metal designs, which means more heat can escape into the surrounding area.

Replacing plastic boxes with metal alternatives will improve the insulation and overall heat sink of your dimmer.

An overabundance of insulation behind your dimmer can also cause a buildup of heat. Remove your faceplate and look for any visible insulation around your dimmer. Use a putty knife to push any excess insulation away from the dimmer unit. This will help your heat to naturally dissipate rather than collect near your dimmer. Be sure to turn off the power to your dimmer before pushing back the insulation. Hitting a live wire with a putty knife can result in shock, short circuits or damage to your dimmer.

Lowering the wattage of your bulbs will also help to reduce heat. 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 cause: 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.

Here are a few ways to combat a noisy dimmer:

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. Compact fluorescent bulbs (CFL) can also cause problems with your dimmer. If you install CFLs, make sure they’re rated as dimmable.

Update your dimmer rating. 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.

It’s best to call a professional electrician to help you choose the correct dimmer replacement.

Consider usage. Running high-voltage bulbs for low-lighting can place extra stress on your dimmer and cause buzzing. Install low-watt bulbs if you keep your lights at a lower setting on a regular basis.

Call a professional if you still notice buzzing. Sometimes, a noisy dimmer is a result of other electrical issues. A pro will help you pinpoint the problem and offer an appropriate solution.