A brief dip in the lights as an air conditioner's compressor starts is common, especially with older units. A flicker that is long, getting worse, or comes with heat, buzzing or tripping is a sign something in the circuit or supply needs attention.
If you're not sure which one you've got, ring 0421 772 661 and we'll test the circuit, the connections and the supply at your switchboard.
If the air conditioner's isolator, a power point or the switchboard smells hot or burnt, looks scorched, or is buzzing loudly, switch the air conditioner off at its controller and stop using it. Turn off the power at the main switch if it is safe to reach, and call an electrician. Call 000 if there is smoke, fire or anyone has had a shock.
Don't open the outdoor unit, the isolator or the switchboard to look for loose wires. The checks below need no covers removed.
An air conditioner's compressor draws a burst of current for a moment as it starts. That current flows through the same wiring, main switch and service cable that feed your lights. If there is any resistance along that path, the voltage dips for an instant and you see it in the lights first, because LED and fluorescent fittings show small voltage changes clearly.
Newer inverter split systems ramp up gently, so they rarely cause a visible flicker. Older fixed-speed units and ducted systems start harder. A tiny, one-off blink can be within normal range. A dip you notice in every room, or one that lasts a second or more, usually points to a weak link somewhere.
None of these need tools or covers off. Note what you find; it helps us narrow it down quickly.
Is it one room, one circuit, or the whole house? Whole-house dips point more toward the main connection or supply; one area points toward a shared circuit.
Look at the switchboard labels. If there's no breaker marked for the air conditioner, it may be sharing a circuit with lights or power points.
Try noticing whether the oven, kettle or dryer causes the same flicker. If several heavy loads do it, the issue is likely upstream of the air conditioner.
If nearby homes see dips at the same times, it may be on Ausgrid's network side. Report it to Ausgrid on 13 13 88.
Without touching inside anything, note whether the switchboard door, the isolator outside or any power point feels warm or smells hot. If so, stop and call us.
Shared circuit. Older installations sometimes have an air conditioner added to an existing power circuit. The start-up load then affects everything else on that circuit. A dedicated circuit is the usual fix.
Loose or tired connections. A loose terminal at the main switch, the air conditioner's breaker, the isolator or the neutral connection adds resistance. It shows up as flicker under load and can heat up over time, so it is worth finding early.
Undersized or ageing supply. Some older Inner West homes still have a small consumer mains cable or an old switchboard that was never designed for today's loads. Big appliances starting together can push it to its limit.
The unit itself. A compressor that is struggling to start, often due to a failing start component, can draw more than it should. That's an air conditioning technician's job; we confirm the electrical supply is sound first.
Call us if the flicker is getting worse, happens throughout the house, comes with buzzing or a hot smell, or if breakers or safety switches trip when the air conditioner starts. Those are signs of a connection or capacity problem, not just a hard-starting appliance.
We measure voltage drop under load, check and tighten connections at the switchboard and isolator, and look at whether your supply and switchboard suit the loads you now run. If the flicker is spreading to other appliances too, our guide to flickering lights covers the wider picture.
A very short, slight dip can be normal with older fixed-speed units. A noticeable or long flicker, or one that is getting worse, should be checked.
Inverter units start more gently and usually cause less disturbance. But if the real cause is a loose connection or an overloaded circuit, a new unit won't fix that.
Brief dips rarely do. The bigger concern is what's causing them: a loose connection can overheat. That's why a worsening flicker is worth testing.
Larger units generally should have a dedicated circuit, and the installation manual states what the unit needs. We can check how yours is wired.
An air conditioning or refrigeration technician. We handle the electrical supply, circuit, isolator and switchboard side.
NSW Electrical Contractor Licence 332956C · Fully insured · Since 2016 · Based in Hurlstone Park
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