Key takeaways
- Check whether the flicker is in one bulb, one fixture, one circuit or the whole house.
- LED bulbs on a dimmer that is not rated for LED are one of the most common causes of flicker.
- Flicker with buzzing, heat or a burning smell points to a loose connection and needs an electrician.
- Whole-house flicker, or lights that go bright in some rooms and dim in others, calls for prompt professional help.
Check the bulb and the fixture first
Begin with the simplest cause. With the light off and the bulb cool, make sure the bulb is screwed in fully. A bulb that has backed out slightly makes poor contact and can flicker, especially when someone walks heavily or a door closes. Swap in a bulb you know works from a lamp that is steady. If the flicker goes away, the first bulb was the problem. If it follows the bulb to the other lamp, discard the bulb.
The bulb type matters. Low-quality or aging LED bulbs flicker as the small driver circuit inside them wears out. Fluorescent tubes and compact fluorescents flicker as they age and more so in cold spaces, such as an unheated garage or porch in an Ohio winter. Bulbs in enclosed fixtures can overheat and cycle on and off. Read the label inside the fixture for its maximum wattage and any rating for enclosed use.
If a new bulb still flickers in the same socket, the socket may be worn, or the small contact tab at the bottom may be flattened so the bulb no longer touches it. Replacing a socket or fixture means working on wiring, so turn off the breaker first, and call an electrician if you are not comfortable doing it.
Dimmers and LED compatibility
Dimmers cause more flickering than almost any other part of a lighting circuit. A dimmer made for incandescent bulbs often does not work well with LEDs, because LEDs draw so little power that the dimmer cannot regulate them smoothly. The signs are flicker at low settings, buzzing, lights that shut off when dimmed, or lights that flash when switched on.
The usual fix is a dimmer rated for LED and bulbs marked dimmable. Look at the dimmer's label for its minimum and maximum load. A dimmer that has only one or two low-wattage LED bulbs on it may be under its minimum, and adding bulbs or choosing a different dimmer can solve it. If several bulbs on one dimmer flicker differently, check that they are all the same model, because different LED bulbs respond differently.
Smart bulbs are a special case. They need steady power to stay connected, so putting them behind a wall dimmer, or turning them off at the wall, can cause flicker or dropouts. Use them in a fixture on a regular switch left on, and control them from the app or a matching smart switch.
A dimmer that is slightly warm is normal. One that is hot, or that buzzes loudly, should be replaced.
Loose connections at switches, sockets and outlets
If several fixtures on one circuit flicker, or the light flickers when you touch the wall switch, bump the fixture, or start a nearby appliance, suspect a loose connection. Wire nuts can loosen, terminal screws on a switch can back out, and connections pushed into the back of an outlet can wear. Each time contact breaks, current can arc across the gap, and arcing makes heat.
That is why a loose connection is a fire risk and not just an annoyance. Warning signs that go along with flicker include:
- A buzzing or sizzling sound from a switch, outlet or fixture
- A switch or cover plate that is warm
- A faint burning smell
- Discoloration around a plate or fixture
If you notice any of these, turn off the breaker and call an electrician. Do not keep using the circuit.
Older homes in Southwest Ohio have had decades of heating and cooling cycles on their connections, and some have aluminum branch wiring or knob-and-tube wiring that needs special handling. Even if you are experienced, turn off the breaker and test that the wires are dead before touching anything. If you open a box and see dark or brittle insulation, scorching or aluminum conductors, close it up and call a professional.
Flicker across the whole house
When lights flicker or dim throughout the house, a bulb is almost never the cause. The common reasons are these.
A large motor starting, such as an air conditioner compressor, a well pump or a sump pump, can cause a short dip. If it is brief and has always happened, it is usually just load on the circuit. If it has become stronger, something has changed.
Storms and the utility's lines. Wind, lightning and fallen branches are part of life in the region and can disturb lines. If your neighbors see the same flicker or lose power, the cause is likely on the utility side, and you should report it to the utility.
A loose neutral connection. This is the one to take seriously. Lights may get very bright in some rooms and dim in others, or flicker and surge when a heavy appliance runs. It can damage electronics and create a fire hazard. The fault may be at the meter, the service cable or the panel. Turn off large appliances and call an electrician right away. If you see arcing or hear sizzling at the meter or the service mast outside, stay away from it and call the utility's emergency line.
Never remove the panel cover yourself. If only your house is affected, an electrician can find out whether the fault is inside the home or at the service connection. Whole-house surge protection is also worth discussing, which is covered under surge protection.
When to call an electrician
Call an electrician when the flicker is not fixed by a new bulb, when it affects more than one fixture, or when it comes with any sign of heat, noise or smell. Call right away if the whole house is affected, if lights are brighter in some rooms and dimmer in others, or if a breaker trips repeatedly.
It helps to note which lights are affected, when it happens (all day, only when an appliance starts, only in storms), how long it has gone on, and whether any switch or outlet is warm or noisy. That lets the electrician go straight to the likely cause.
For repairs, see electrical repair or contact us. For the wider picture on outlets, dimmers and fixtures, see the home lighting guide.
Frequently asked questions
Why do my LED lights flicker when dimmed?
Most often the dimmer is not rated for LED, the bulb is not dimmable, or the total load is below the dimmer's minimum. Matching a dimmable bulb with an LED-rated dimmer within its load range usually solves it.
Do flickering lights mean there is a fire hazard?
Not always. A loose bulb or an old dimmer is harmless, but flicker from a loose connection can create arcing and heat. If flicker comes with buzzing, a warm switch or plate, or a burning smell, turn off the breaker and call an electrician.
Is it normal for lights to dim when the AC starts?
A brief, slight dip when a large motor starts can be normal. If the dip is large, getting worse, or affects the whole house, have an electrician check the connections and service.
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