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Air Conditioner Turns On By Itself

Imagine you’re home alone, relaxing and winding down from a busy day.  The temperature has dropped since the sun went down, and there’s no longer a need for the AC to be pumping out cold air.  You turned the air conditioner off about an hour ago, and now ready to snuggle down and watch an episode (or two) of your favourite show.

All of a sudden, the air conditioning comes on!  You look at the controller, thinking ‘did I turn that on?’.  No, not me.  Then you look around for company, thinking ‘is someone here?’.  No, no one there.  Then you start to imagine what else it could be… Stalker?  Ghost?  Poltergeist?

It can be quite scary when you air conditioner turns on by itself.  Normally we worry about it turning off when we need it most, but having an aircon turn on itself can be just as frightening.

Fear not!  There may be a more practical reason why your AC automatically turns on (or off) without anyone or anything touching it.  Firstly, it may be a sign that you’re in need an air conditioner repair service.  A full service is recommended by a professional at least once a year at home and as often as monthly in the workplace.  It’s also worth ensuring your home air conditioner service and maintenance tasks are up to date.

In this article we’ll explore common reasons why your AC may turn on randomly and what you can do about it.  Many of the causes and solutions apply to commercial air conditioning as well as home air conditioning.

This week’s question:  

Why does my aircon turn on by itself?

Surprisingly, there can be many possible issues that can cause an aircon to turn on by itself.  Here are some common reasons and what can be done about them:

Incorrect temperature settings may cause random on/offs of an AC

A seemingly random activation of the AC can be due to incorrect temperature settings.  Programming the temperature settings to suit the season can help prevent this issue (e.g. 24 degrees on cooling mode in Summer, 18 degrees on heating mode in Winter).

Power saver or sleep mode activation may cause auto-on air conditioning

These modes are designed to save electricity by intermittently turning the AC on and off at given times.  Understanding and adjusting these settings can help manage these features more effectively.  It’s recommended to check the AC manual, or ask a Service Technician when onsite.

Lady changing settings on air conditioning controller


Faulty controller or thermostat can signal automatic turn on of an AC system

Faulty temperature readings from a thermostat (stand alone or in the form of a controller) can not only misrepresent the temperature but also turn systems on randomly.  Check batteries first, then look at how to reset air conditioner thermostat.  If no luck, you may need controller repair or replacement.

Misaligned thermostat or sensor may cause random functioning

A thermostat/controller or sensor placed near an air vent or in direct sunlight can incorrectly trigger an air conditioner to turn on and off incorrectly.  Proper placement of a temperature-detecting controller, thermostat, or sensor is essential for accurate temperature regulation.

Short cycling of large aircon units can cause frequent turn-ons.

Oversized AC units (in terms of kW capacity) may short cycle the system, leading to inconsistent cooling and frequent on/off cycles.  Ensuring an air conditioner size matches the area served is crucial.

Dirty air filter can impact cycling

A clogged air filter can impede airflow, causing an air conditioner to short-cycle and turn on and off repeatedly.  Regular checking, cleaning, and replacement (when required) of return air filters is advised.  If not sure how to clean air conditioning filters, an HVAC technician can show you how.

AC condenser coil issues may cause system to turn off and on sporadically

Short cycling due to blocked condenser coils, like the effects of clogged air filters, can disrupt normal operation.  Regular inspection and cleaning of coils when required is recommended as part of routine air conditioning maintenance.

Compressor overheating can result in spontaneous AC turn-on

If an AC compressor overheats due to being unclean, faulty, or other issue, it may lead to self-shutoff.  Once it has cooled down, it may kick back in and air conditioner resumes.   Keeping the compressor clean and well-maintained is important as it has a major role in how an air conditioner works.

Refrigerant issues may trigger an air conditioner to turn on and off right away.

A refrigerant leak or failure of any refrigerant-related components can cause an AC unit to turn on and off straight.  Prevention is better than cure in this scenario, which is why it’s important to service air conditioning routinely.

Iced up coils can cause AC cycling

Frozen evaporator coils can cause an air conditioner to cycle sporadically.  Addressing the underlying cause for the ice may be as simple as filter and coil washing.  However, something like a refrigerant leak will require the expertise of an HVAC professional to resolve.

Safety switch activation can turn on an air conditioner

Frequent tripping of the circuit breaker or fuse can result in an aircon cycling on and off.  This safety feature requires professional assessment to identify underlying electrical issues.  A qualified HVAC Technician typically holds a restricted electrical licence that allows them to investigate electrical circuits connected to an air conditioner.

AC component failures can cause air conditioning to turn on/off at random

Defective wiring, fans, motors, compressors, condensers, relays, timers, and electronic control boards can all cause erratic air conditioner behaviour.  Professional diagnosis and repairs are necessary for these complex issues.

HVAC Technician inspecting outdoor air conditioner unit for ac repair service


While the AC turning off can be terrifying, the turning on of an aircon at random can be just as frightening.  Fortunately, there are many of things you can check yourself, at home or at work.

A few basic checks, regular maintenance, and timely intervention by a professional are all key in preventing or treating an air conditioner turning on unexpectedly.  If you need a professional or to discuss further, contact your local air conditioning company.


Which brand of AC automatically turns off and on the most?

Most commonly the AC automatically turns off and on with electronics-based devices, including but not limited to:

  • Panasonic
  • Samsung
  • LG

These brands all specialise in products such as TV’s and smart appliances.  With an electronic-based item, it’s no surprise that the system may do the old reset trick: off and on again to get it working properly.

This phenomenon also affects cheaper brands that also often manufacture whitegoods, including but not limited to:

  • Kelvinator
  • Midea
  • Carrier

Midea is a particularly interesting brand as it manufactures many other aircon brands today, including Samsung, LG, Lennox, and even Carrier (whose founder is considered the inventor of modern air conditioning).

Other brands of air conditioning can also automatically turn off and on, including Daikin, Mitsubishi Electric, MHI, Rinnai, etc.  However, it isn’t as common as with the other brands mentioned above.


Why does my air conditioner turns off by itself?

Many of the reasons why an air conditioner turns on by itself are the same as why an air conditioner turn off by itself.  This includes, but is not limited to:

  • Wrong mode or temperature settings.
  • Sleep or Eco Mode programmed incorrectly.
  • Faulty thermostat or controller.
  • Poorly positioned temperature-sensing device.
  • Oversized air conditioning capacity (kilowatts).
  • Dirty return air filter.
  • Blocked condenser coil.
  • Overheated compressor.
  • Refrigerant-related issues.
  • Iced up coils.
  • Safety switch activation.
  • AC component failure.

Addressing these issues through regular maintenance such as filter cleaning and program setting can be helpful.  However, refrigerant level checks, component testing, and electrical assessments all call for a professional to prevent complications and damage to yourself or the system.


Stop the scare and get your air conditioner working as it should today; book air conditioner repair service today.