Air conditioners rely on a steady and safe electrical supply to work properly. When something goes wrong electrically, the system may stop working, trip the power, shut down without warning, or give off warning signs like burning smells or error codes.
In Perth homes, many aircon faults are electrical rather than mechanical, and they often come from power supply issues, ageing components, or installation problems. Knowing the common electrical problems and what they mean helps you act early, avoid safety risks, and get the right professional help before damage gets worse.
Below, we break down the most common electrical air conditioning problems, explain why they happen, and outline what to do when they occur.
| WA safety note: In Western Australia, DIY electrical work is dangerous and should not be done. By law, electrical work on your home must be carried out by a licensed electrician (or appropriately licensed technician). |
Key Summary: Common Electrical Problems in Aircons
- Air conditioner will not turn on
- Circuit breaker or safety switch keeps tripping
- Outdoor unit not running
- Contactor failure
- Capacitor failure
- Air conditioner turns off by itself
- Thermostat or thermostat wiring fault
- Control board failure
- Communication faults between indoor and outdoor units
- Burning smell from the air conditioner
- Air conditioner trips power on startup
- Undervoltage or poor power quality
- Incorrectly sized electrical circuit
- Loose or degraded wiring and terminals
- Moisture-related electrical faults
- Age-related electrical degradation
- Error codes and warning lights
1. Air conditioner will not turn on
This fault occurs when electrical power is interrupted before it reaches the system, which completely prevents the air conditioner from operating even if the unit itself is not mechanically faulty.
This is one of the most common electrical aircon problems and usually points to a loss of power somewhere between the switchboard and the unit.
Typical causes:
- Tripped circuit breaker or blown fuse
- Faulty isolator switch
- No power supply to the unit
- Failed control board
- Loose or damaged wiring
What to do:
- Check the breaker and isolator are ON (no opening anything).
- If it still won’t start, leave it off and book a licensed electrician/tech.
2. Circuit breaker or safety switch keeps tripping
This happens when the air conditioner draws unsafe current or electricity leaks to earth, causing the protection device to cut power to prevent overheating, damage, or fire.
Frequent tripping is a warning sign that should never be ignored or repeatedly reset.
Common electrical reasons:
- Short circuit inside the unit
- Overloaded circuit
- Faulty compressor drawing excess current
- Moisture inside electrical components
- Undersized wiring or breaker
What to do:
- Stop resetting it repeatedly.
- Switch the system off at isolator.
- Leave the breaker OFF and call a licensed electrician.
3. Outdoor unit not running
This fault means electrical power is not being correctly delivered to the outdoor components, stopping the compressor from operating and preventing heating or cooling.
The indoor unit may still run and blow air, but without the outdoor unit there is no temperature control.
Electrical causes include:
- Failed contactor
- Faulty capacitor
- No power to the outdoor unit
- Safety cut-out activated
- Loose terminals or burnt connections
What to do:
- Turn system off.
- Check isolator is ON and note any error code.
- Book a licensed electrician/tech to test supply and controls.
4. Contactor failure
A contactor failure prevents electrical power from being switched through to the compressor, leaving the system powered but unable to start under load.
This fault often goes unnoticed until electrical testing is carried out.
What happens:
- Power is present but not passed through
- Outdoor unit remains completely inactive
What to do:
- Turn unit off and don’t keep trying to start it.
- Book a licensed tech to test and replace parts.
5. Capacitor failure
When a capacitor fails, motors cannot receive the electrical boost needed to start, which causes hard starts, tripping, or complete failure to run.
This is one of the most common electrical faults in residential air conditioners.
Symptoms include:
- Unit hums but does not start
- Compressor or fan struggles to engage
- Circuit trips during startup
What to do:
- If it hums or struggles, turn it off.
- Do not restart repeatedly.
- Book a licensed tech.
6. Air conditioner turns off by itself
This occurs when electrical protection systems detect unsafe conditions and shut the unit down to prevent component damage.
The shutdown may appear random but is usually triggered by a measurable electrical issue.
Possible reasons:
- Overheating electrical components
- Loose wiring
- Faulty sensors
- Control board errors
- Voltage supply problems
What to do:
- Note when it happens and any error code.
- If it repeats, stop using it and book a licensed tech.
7. Thermostat or thermostat wiring fault
Faulty thermostat wiring sends incorrect electrical signals, causing the air conditioner to make the wrong decisions about when to start, stop, or cycle.
This issue can easily be mistaken for a performance or temperature problem.
Electrical signs include:
- Ignoring temperature settings
- Short cycling
- No response to control changes
What to do:
- Replace remote batteries if applicable.
- Note symptoms and error codes.
- Book a licensed tech to test controls and wiring.
8. Control board failure
A failed control board disrupts the electrical commands that manage every function of the air conditioner, leading to unpredictable behaviour or total shutdown.
Modern systems rely heavily on electronics, making this fault increasingly common.
Causes include:
- Power surges
- Moisture damage
- Age-related component failure
This can affect:
- Starting and stopping
- Temperature regulation
- Communication between units
What to do:
- Turn it off if behaviour is erratic.
- Note error codes/lights.
- Book a licensed tech.
9. Communication faults between indoor and outdoor units
This fault occurs when electrical communication signals between the indoor and outdoor units are interrupted, preventing them from operating in sync.
It is particularly common in inverter and newer split systems.
Electrical causes:
- Broken communication wiring
- Incorrect voltage supply
- Failed control boards
Often shown as error codes or flashing lights.
What to do:
- Record the exact error code.
- Power the system off and leave it off if it repeats.
- Book a licensed tech.
10. Burning smell from the air conditioner
A burning smell indicates overheating or electrical arcing, which can quickly lead to serious equipment damage or fire risk.
This should always be treated as urgent.
Electrical causes:
- Overheating wiring
- Burnt terminals
- Failing motors
- Melted insulation
What to do:
- Turn it off immediately.
- Switch off at isolator or breaker.
- Do not use again until inspected by a licensed electrician.
11. Air conditioner trips power on startup
Startup draws the highest electrical load, and if components cannot handle it the safety system cuts power immediately.
This issue often appears suddenly, even if the unit worked previously.
Common reasons:
- Weak or failed capacitor
- Ageing compressor
- Undersized electrical circuit
- Poor supply voltage
What to do:
- Stop attempting restarts.
- Leave breaker off if it trips again.
- Book a licensed electrician to test the circuit and unit.
12. Undervoltage or poor power quality
Low voltage forces the air conditioner to draw higher current to compensate, which increases heat, stress, and failure rates.
This problem often originates from the home’s electrical system rather than the air conditioner itself.
Causes include:
- Long cable runs
- Older switchboards
- Shared circuits
- Utility voltage drops
What to do:
- Note timing (hot afternoons, peak load).
- Stop using the unit if faults repeat.
- Book a licensed electrician to test supply and circuit.
13. Incorrectly sized electrical circuit
An undersized circuit cannot safely supply the current the air conditioner needs, leading to ongoing electrical stress and repeated faults.
This is usually an installation issue that only becomes obvious over time.
Results include:
- Frequent tripping under load
- Overheating cables
- Shortened component life
What to do:
- Do not change breakers or “upgrade” anything yourself.
- Stop using it if tripping continues.
- Book a licensed electrician to assess the circuit.
14. Loose or degraded wiring and terminals
Loose or damaged wiring increases electrical resistance, creating heat build-up that leads to intermittent faults or safety risks.
This is especially common in older systems and installations.
Includes:
- Brittle insulation
- Corroded terminals
- Burnt connections
- Poor original workmanship
What to do:
- If you notice burning smell, buzzing, or repeated trips, switch off.
- Book a licensed electrician to inspect.
15. Moisture-related electrical faults
Moisture creates unintended electrical paths that trigger safety devices and cause corrosion-related failures.
Outdoor units are particularly vulnerable to this type of fault.
Moisture can cause:
- Short circuits
- Earth leakage trips
- Corrosion on boards and terminals
What to do:
- If it started after heavy rain or washing down, switch off.
- Do not try to dry/open the unit.
- Book a licensed tech to inspect.
16. Age-related electrical degradation
Over time, electrical components lose efficiency and reliability, even when the air conditioner still appears to function normally.
Electrical wear often occurs long before mechanical failure.
This includes:
- Capacitors weakening
- Contactors pitting
- Control boards failing
- Wiring insulation breaking down
What to do:
- If the system is older and faults are increasing, book a preventative inspection.
- Discuss repair vs replacement with a licensed pro.
17. Error codes and warning lights
These appear when electrical readings fall outside safe operating ranges, signalling faults before major damage occurs.
They are indicators, not fixes, and still require proper diagnosis.
These usually indicate:
- Power supply issues
- Sensor faults
- Communication errors
- Control board problems
What to do:
- Write down the code.
- Turn the unit off if the fault repeats.
- Book a licensed tech and give them the code.
Have a problem that needs fixing? Contact an electrician for a consultation and assessment
Electrical problems in air conditioners should never be ignored. Issues like repeated tripping, burning smells, units cutting out, or outdoor systems not running can point to unsafe electrical conditions that only get worse over time.
While homeowners can safely turn systems off and note what is happening, electrical testing and repairs must always be carried out by a licensed electrician or authorised air conditioning technician in WA. Attempting DIY electrical work is unsafe and illegal.
If your air conditioner is showing any of the issues covered above, we recommend having it checked early to prevent breakdowns, fire risk, or costly damage.
Need help with an aircon servicing and repairs in Perth?
Contact Limelight Electrix today. We provide clear advice, upfront pricing, and a free electrical safety check with every service, so you can get your home back to safe and reliable cooling with confidence.
