Why Are My Lights Flickering?

One bulb flickering on its own is almost always harmless. Lights flickering across the whole house, a buzzing or crackling switch, or lights dimming every time the air conditioner starts is a different problem, and it needs a licensed electrician today. All of it is a symptom of voltage fluctuation, and the cause ranges from a bulb and dimmer mismatch through to loose wiring behind your walls.

A quick note before you start: if the lights look steady to everyone else in the room but you are seeing flickering, flashing or shimmering in your vision, that is not an electrical problem. Visual flickering can be an early sign of a retinal tear or an eye stroke. Stop reading and seek medical attention.

Can flickering lights be a fire hazard?

Flickering becomes a serious fire risk when it is caused by arcing. Arcing happens when current jumps a gap at a loose or corroded connection instead of flowing cleanly through the conductor. The arc generates intense localised heat inside a wall cavity, ceiling space or switch. Nobody can see it. Nothing is there to stop it spreading.

That is why electricians treat flickering as a symptom rather than an annoyance. The flicker you can see is the visible end of a fault you cannot.

The 10 second threat level test

Work through these three groups and find the one that matches what your house is doing.

Red alert. Turn the switch off and call an electrician now.

• Lights flicker in more than one room
• Lights dim or flicker whenever the air conditioner, microwave, kettle or pump starts
• You can hear buzzing, crackling or sizzling from a switch, powerpoint or fitting
• A switch plate, powerpoint or light fitting feels warm or hot to touch
• You can smell anything sharp, plastic or burnt near a fitting

If any of these apply, this is a job for an emergency electrician rather than something to leave until the weekend.

Amber alert. Sort it out today.

• Flickering is limited to one fitting or one switch
• A circuit breaker trips now and then for no obvious reason
• The light only flickers when you touch or bump the switch

Green alert. Almost certainly harmless.

• One bulb flickers and the rest of the house is fine
• LED bulbs flicker on an older dimmer
• LED lights flicker briefly at the same time each evening and nothing else in the house is affected

What to do in the next sixty seconds

1. Turn off the wall switch controlling the flickering light.
2. Hold the back of your hand near the switch plate and the fitting. Do not press hard, and do not remove anything. You are checking for abnormal warmth.
3. Stand still and listen. Faint buzzing or crackling from inside the wall or fitting is the sound you do not want to hear.

If anything in the red alert list applies, leave that switch off and stop using the circuit until an electrician has been through it.

How to troubleshoot flickering lights step by step

These four checks let you narrow down the cause without opening anything up or touching wiring. Nothing here needs a tool. In NSW, anything past changing a bulb is licensed electrical work, so these steps are about diagnosis, not repair. Knowing which of the four tests produced the flicker means the electrician arrives already halfway to the answer.

Step 1. The bulb tighten and swap test

What to do: turn the light off at the wall and give the bulb five minutes to cool. With a gloved hand or a dry cloth, tighten the bulb a quarter turn. Turn it back on. If it still flickers, swap it for a bulb you know works, ideally a different type to the one you pulled out.

What it tells you: this is the cheapest thing on the list to rule out and it costs you nothing but a spare globe. If a fresh bulb fixes it, you are done. If the same flicker follows the new bulb, the problem is the fitting, the switch or the circuit, and the rest of these steps are worth your time.

Watch for this: LED bulbs on a dimmer built for old incandescent globes flicker constantly and it is not a fault. LEDs draw so little power that older dimmers cannot regulate them smoothly. The fix is an LED compatible dimmer, which is work for a licensed electrician. If you are partway through an LED lighting upgrade, the dimmers need to be part of the job rather than an afterthought.

Step 2. The appliance load test

What to do: turn the flickering light on. Now switch on something with a heavy start up draw, such as a vacuum, hair dryer, microwave or air conditioner.

What it tells you: if the light dims noticeably or flickers hard the moment that appliance starts, the circuit is carrying more than it comfortably should. This is usually accumulation rather than a fault. A house wired in the 1980s was wired for a household where air conditioning was the exception, and ABS figures reported by the Australian Government put penetration at around a quarter of Australian homes through the mid 1980s and 1990s, rising past half by 2008 and to 58 per cent by 2014. The wiring did not change. What you plug into it did.

The answer is a dedicated circuit for the heavy appliance, and often a switchboard upgrade to make room for it. Our guide to electrical load capacity explains how to work out what your existing circuits can actually carry.

Step 3. The switch wiggle test

What to do: with the light on, gently move the switch toggle. Gently. You are not trying to force anything, and you should not be removing the plate.

What it tells you: if the flicker follows your hand, the switch contacts are worn or a connection behind the plate has worked loose. Both are ordinary wear. A switch that has been operated several times a day for thirty years is a mechanical device at the end of its life, and worn contacts are one of the more likely places for arcing to start. This one does not wait. Replacing powerpoints and switches is a small job compared with what a neglected one can turn into.

Step 4. The switchboard check

What to do: open the switchboard door and look. That is all. Check whether any circuit breaker is sitting halfway between on and off, and whether anything is discoloured, scorched or smells warm. Do not remove the cover, and do not pull, prise or reseat anything.

If you find a breaker that has clearly tripped, you can reset it once. If it trips again, leave it off and call an electrician. A breaker that keeps tripping is doing its job and telling you something.

What it tells you: an older ceramic fuse board or a switchboard with no safety switches has no way to detect the kind of fault that causes flickering. Safety switches became mandatory on power circuits in new NSW installations in 1991, and on lighting circuits from 2000. If your home predates that and has never had the switchboard touched, there is a good chance nothing in it is watching for earth leakage at all. In that case the flickering is the second problem and the switchboard is the first.

If it happens at the same time every night

There is one cause of flickering that is close to unique to this part of the country, and it is not a fault in your house at all. Ausgrid and Endeavour Energy send control signals down the network to switch off-peak hot water systems and street lights on and off. These signals are superimposed on the normal 50 Hz supply at frequencies between 167 and 1050 Hz depending on where you are, and the frequencies used in each area are set out in the NSW Service and Installation Rules.

Old incandescent globes ignored them. LED drivers often cannot, and the research centre that studies this documents the signals interfering with the operation of electronic dimmers attached to LED lights. The same signals are why some people hear a faint hum from a ceiling fan at night.

The tell is timing. If the flicker arrives at roughly the same time each evening, lasts a short while, affects LED fittings and leaves everything else in the house alone, this is almost certainly what you are seeing. A filter fitted to the lighting circuit is the usual fix.

Why “leave it and see if it settles” is the wrong instinct

A loose connection does not sit still. Once the contact is no longer tight, resistance at the junction creates localised heat, the heat accelerates oxidation and metal creep, the connection works looser still, and it heats further. Fire researchers describe it as an unstable positive feedback loop, and it only runs in one direction. Left alone, the junction can reach the stage known as a glowing connection, where copper oxide at the contact point sits at roughly 1250 degrees Celsius inside your wall cavity.

Two figures from the laboratory work make the point better than any warning could. Carrying the same 20 amp load, a sound connection gives off something like a tenth of a watt as heat. A failing one gives off 20 to 40 watts, concentrated in a space the size of a screw terminal. And in testing at the US National Bureau of Standards, a glowing connection was recorded running continuously for 129 hours. There is no point at which it exhausts itself and stops.

Switch it off and leave it off.

Why is my power flickering but the circuit breaker has not tripped?

This is the part that catches people out, and the answer is not reassuring.

Circuit breakers are built to detect two things: too much current flowing through the circuit, and a short circuit. They are very good at both. What they cannot see is a loose connection. Current across a poor connection can arc, heat and flicker for months while staying well under the threshold that would trip the breaker or blow a fuse.

The mechanism behind this runs opposite to intuition. When a connection fails in series with the load, the arc that forms across the gap adds resistance. That means current in the circuit goes down, not up. Fire researcher Vytenis Babrauskas states it directly in his review of wiring fault ignition: with a series arc, an overcurrent protection device cannot be expected to respond. Your breaker is watching for too much current. A failing connection hands it less.

The same body of research ranks the physical mechanisms behind electrical fires in order of importance, and poor connections sit at the top of that list. Overload, the thing your switchboard is actually built to catch, does not make the top group. Testing suggests it takes an overload of roughly three to seven times the rated load to start a fire that way, which is far beyond what a normal household circuit sees.

A breaker that stays put during a flickering event is not evidence that everything is fine. It means the fault is a type your switchboard is not equipped to detect.

The other common causes of flickering with no trip are a voltage drop across undersized or ageing consumer mains, a loose neutral connection at the switchboard, and supply side issues on the network itself. That last one is worth ruling out early. If your neighbours’ lights are flickering at the same time as yours, the problem sits with the network, not your house.

Arc fault detection devices, which sense the electrical signature of arcing and cut power, are the technology built specifically for this gap. They are worth raising as part of any switchboard upgrade, and the case gets stronger the older the wiring is. Testing on wiring pulled out of real houses found no meaningful age effect until wiring passes roughly thirty to forty years, after which insulation performance drops away. Rubber-insulated VIR cable installed before the 1960s, which we still find in Western Sydney homes that have never been rewired, was often found crumbling outright. Where that is what is behind your walls, a house rewire is the real answer rather than another patch.

Should you fix flickering lights yourself or call an electrician?

In NSW the answer is narrower than most guides suggest. Changing a bulb is yours. Resetting a tripped breaker is yours. Everything else, including swapping a dimmer or replacing a light switch, is licensed electrical work under NSW law. It is not a grey area and it is not about difficulty.

While you wait

Unplug computers, televisions and anything else expensive from the affected circuit. Unstable voltage is hard on anything with a circuit board in it, and a surge will find the expensive things first. Keep the affected switch off, and if you have smelled burning or found heat at a fitting, turn that circuit off at the switchboard entirely.

If you are not sure how much of your wiring is in this condition, an electrical safety inspection will tell you where you stand before you spend money guessing.

Get it looked at properly

Moonlight Electrical is a family owned and operated business working across Western Sydney. We hold NSW Electrical Contractor Licence 373818C. We are also Level 2 ASP accredited, which means we can work on the connection between the network and your property, not just the wiring inside it.

We are available 24 hours a day, seven days a week for electrical emergencies. Book before midday and we will be there within 60 minutes or the service call is free. We quote per job, not per hour, so you know the cost before we start. All workmanship is backed by our Lifetime Labour Guarantee. Electrical systems carry a 7 year warranty. Seniors receive 10% off.

Call 0401 019 632 and we will find out what is behind the flicker.