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Power Supply Check
We test the switchboard, isolator, and main power supply to confirm the system is receiving electricity correctly.
Find the fault. Restore power. Get your system running again.
Air Conditioner Not Turning On?
Common AC Problems
What Causes an Air
Conditioner Not to Start?
If your air conditioner isn’t turning on, the issue is often related to power supply, settings, or an internal system fault. In many cases, it’s something simple that can be identified quickly with a basic check. A dead system is one of the most common faults we’re called out to across Sydney, and the vast majority are back up and running the same day once the root cause is identified — either as a straightforward fix or as part of our full air conditioning repairs service.
However, it can also indicate a deeper electrical or component issue that needs proper diagnosis to prevent further damage and restore safe operation. If it’s the middle of summer and you can’t wait, our emergency air conditioning repairs team prioritises no-start and no-cooling callouts — especially for elderly residents, young children, and anyone medically vulnerable.
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Years of Industry Experience
Licensed, Certified & Insured Technicians
Environmentally Responsible & ARCtick Certified
100% Service Satisfaction Guarantee
Flexible & Affordable Financing Options
Wide Range of Systems & Leading Brands
Quick Checks First
Before You Book a Service
Check the controller
Ensure the system is switched on and set correctly. If the display is blank, it may not be receiving power.
Check the remote batteries
If you’re using a split system with a handheld remote, flat batteries can stop the system from responding.
Check the power supply
Look at the switchboard and see if the circuit breaker has tripped. If it has, reset it once and check if the system starts.
Check the isolator switch
Most outdoor units have an isolator nearby. Make sure it hasn’t been accidentally switched off.
Try a full reset
Turn the system off at the controller, isolate power at the breaker for a few minutes, then turn everything back on. Allow at least 10 minutes for the system to restart and stabilise before judging the result.
If the System Is Still Not Turning On
If the unit is still not responding after completing the basic checks, the issue is likely technical and will require a proper inspection. The fix depends on whether you have a split system or ducted system — the diagnostic steps and common failure points are different for each.
Common causes include:
- Electrical faults or blown internal components
- Faulty control or circuit boards
- Safety switches tripped due to an underlying fault
- Damaged wiring or loose electrical connections
- Compressor or fan motor failure preventing startup
These issues typically cannot be resolved with basic resets and require diagnostic testing to accurately identify the root cause and prevent further damage.
What it means for your system: when an aircon won’t turn on, electricity is either not reaching critical components, or a safety system has shut the unit down to prevent damage. Either way, forcing restarts puts stress on the compressor — the most expensive single component in the system. A $300 capacitor replacement caught early becomes a $2,500 compressor job if ignored.
When it becomes serious: if the breaker keeps tripping immediately after reset, if you smell burning or see any sign of heat damage around the outdoor unit, or if the system has been unresponsive for more than 48 hours in hot weather. These are signs of electrical faults that can worsen quickly. Stop attempting to restart and call a licensed technician — repeated resets on a faulty system are a known cause of both compressor failure and, in rare cases, electrical fires.
Units that were displaying error codes or making unusual noises before they stopped are often showing early signs of a developing fault. Check our guide to high power bills too – a failing compressor can draw excessive current before it fails completely.
Common Factors
Common Start-Up Problems
If your system still isn’t starting, the issue may fall into one of several common fault types. These quick indicators can help narrow down what might be wrong before a technician inspection is required. Many of these overlap with other symptoms — if your system starts but then fails to cool, check our not cooling diagnostic guide instead, and for systems blowing the wrong temperature see not heating in winter mode.
No power to the system
This is often caused by a tripped circuit breaker, a switched-off isolator, or an electrical supply fault.
System beeps but does not start
This may indicate a control issue, faulty sensor, or internal communication error between components.
Circuit breaker trips when turning on
This usually points to an electrical fault. Do not keep resetting the breaker, as it may cause further damage.
System completely unresponsive
This can be caused by a failed internal component, faulty control board, or issues with the power supply.
When to Stop Trying
If the system continues to trip the breaker, remains completely unresponsive, or shows signs of electrical issues, stop attempting further restarts and arrange for a professional inspection.
Repeatedly resetting power can worsen the fault and may lead to additional damage to internal electrical components.
Diagnosis Process
How We Diagnose the Issue
When a system is not turning on, we follow a structured diagnostic process to accurately locate the fault instead of relying on guesswork.
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Voltage Testing
We measure voltage levels to ensure stable and correct power is reaching the unit.
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Wiring & Connection Inspection
All wiring and terminal connections are checked for damage, looseness, or signs of wear.
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Control System Testing
We inspect and test control boards, sensors, and communication signals between components.
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Component Diagnosis
We identify any failed, shorted, or faulty parts that may be preventing the system from starting.
Choose the Right Fix
Repair or Replacement
We help you make the right decision based on cost, condition, and long-term reliability.
When a system won’t turn on, the issue is often electrical. Many faults — such as wiring issues, failed components, or control problems — can typically be repaired once the root cause is identified, usually for a fraction of replacement cost. See our pricing and costs guide for typical repair ranges.
However, if the problem involves major components like control boards or compressors, particularly in older systems, repair costs can increase significantly. Regular preventative maintenance catches most of these faults before they become no-start emergencies — things like capacitor wear, loose terminals, and early compressor strain are all visible during a standard service.
However, if the problem involves major components like control boards or compressors, particularly in older systems, repair costs can increase significantly.
The best option usually depends on:
- System age
- Availability of replacement parts
- Overall condition of the unit
- Repair cost compared to system value
If the cost of repair begins to approach the cost of replacement, upgrading the system is often the more practical and reliable long-term choice.
We always present both repair and replacement options clearly, so you can make a confident and informed decision.
Get Your Air Conditioner Running Again
If your air conditioner is not turning on, the next step is a proper diagnosis. We can inspect the system, identify the exact cause of the fault, and recommend the most suitable repair or replacement option.
Book an inspection to get your system checked and back up and running with confidence.
FAQS
Need help? We’ve got your answer
A completely dead system almost always comes back to one of five things: a tripped circuit breaker at the switchboard, a blown fuse, an isolator switch accidentally turned off near the outdoor unit, a faulty controller or flat remote batteries, or an internal electrical fault like a failed capacitor, contactor, or control board. Quick sanity checks: confirm the breaker hasn’t tripped, check the isolator switch outside, and try fresh batteries in the remote. If the unit is still completely unresponsive after those checks, there’s an internal electrical fault that needs a licensed technician. Don’t keep cycling the power — it can worsen the fault.
No — and this is important. A circuit breaker trips to protect you and the house wiring from an electrical fault. Repeatedly resetting it doesn’t fix anything; it simply forces current through a known fault, which can damage the system further and, in worst cases, create a fire or shock risk. If the breaker trips once and the system runs normally after, it may have been a one-off surge. If it trips a second time, leave it off and arrange an inspection. The fault could be a failed capacitor, a short in the compressor, water ingress, or damaged wiring — all of which need licensed diagnosis.
Yes — and it’s one of the most common “false alarm” callouts we get. If your split system is controlled by a handheld remote, flat or weak batteries can stop signals reaching the indoor unit even though the system itself is working perfectly. Replace with fresh alkaline batteries (not rechargeables, which run at a lower voltage) and try again within a metre or two of the unit. If the unit still won’t respond, the fault is likely with the remote itself, the infrared receiver inside the indoor unit, or the controller board. A technician can test all three and replace whichever has failed.
No — the vast majority of no-start faults are repairable once the exact cause is identified, and replacement is rarely the first option. Typical fixes include replacing a blown capacitor ($200-$400), a failed contactor, a faulty controller or PCB, resetting a safety lockout triggered by an overheated component, or repairing damaged wiring. Full system replacement is only genuinely warranted when a major component like the compressor or condenser fan motor has failed on an older unit (12+ years old) where the repair cost approaches the replacement cost. We’ll always give you a clear side-by-side comparison before you make that call.
Short-cycling — where the system fires up then shuts down within seconds or minutes — is almost always a protective response to an underlying fault. Common causes include a failing capacitor that can’t sustain compressor start-up, a clogged filter causing the indoor coil to overheat, low refrigerant tripping a safety sensor, a faulty thermistor misreading temperature, or a failing compressor drawing excessive current. Running the system in this state puts serious strain on the compressor with every restart — switch it off at the controller and breaker, and book an inspection. Diagnosing short-cycling early is usually a $200-$500 repair; ignoring it often becomes a compressor replacement.
We prioritise no-start, no-cooling, and no-heating callouts — in most Sydney suburbs we can have a licensed technician onsite the same day or the next business day. During heatwaves or cold snaps when demand spikes, we run priority response for elderly residents, young children, and anyone with health conditions — see our emergency repairs service for after-hours callouts. Our vans carry common parts — capacitors, contactors, thermostats, control boards — so many no-start faults can be diagnosed and repaired on the first visit. Call (02) 9820 4500 and we’ll book the earliest available slot.
Five quick checks that solve a meaningful percentage of no-start callouts before you pay for a diagnosis: (1) Thermostat or remote — fresh batteries, correct mode selected, temperature set appropriately. (2) Main circuit breaker at the switchboard — look for one in the middle position or flipped to off, reset it once. (3) Isolator switch near the outdoor unit — these get bumped or turned off by accident more often than you’d think. (4) Power at the wall outlet if it’s a plug-in unit. (5) Full reset — turn off at the controller, kill power at the breaker for 5 minutes, restore power, wait 10 minutes for the system to initialise. If none of those revive it, there’s an internal fault and you’ll need a technician.
Ducted systems often need a full power reset after a blackout or brownout because the control board can lock into an error state when voltage drops suddenly. The fix most homeowners can try: turn the system off at the wall controller, then isolate power at the main breaker for at least 5 minutes, then restore power and wait 10 minutes before attempting to restart. If it still won’t start, the outage may have damaged the control board, a transformer, or a capacitor — all common casualties of power surges. This is a ducted-specific fault we see regularly in Sydney after summer storms. Fitting a surge protector to your switchboard prevents repeat damage and is worth considering if outages are frequent in your area.
Yes, and a full reset resolves a surprising number of no-start issues caused by transient faults or power fluctuations. The correct sequence: (1) Turn the system off at the wall controller or remote. (2) Go to the switchboard and flip the AC circuit breaker to off. (3) If there’s an isolator switch near the outdoor unit, turn that off too. (4) Wait a full 5 minutes — this lets capacitors discharge and the control board clear any error state. (5) Restore power in reverse order: isolator first, then breaker, then controller. (6) Wait 10 minutes before judging whether it’s working. If the system still won’t start after a full reset, the fault is internal and needs a technician.