Air Con Malfunctions

11 common air conditioner problems & how to fix them

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When your air conditioning unit stops working, it might be a simple fix. But it can also be a major issue. While some problems can be avoided with regular cleaning, it’s important you have a technician look at the issues you can’t solve yourself. There are a variety of reasons that can set your air con off, so let’s have a look at some of the most common air conditioner problems and how to fix them.

11 common air conditioner problems

Want to know how to fix your air conditioner? Here are 11 common problems with home air conditioners and how to fix them:

Let’s take a closer look at each of these air conditioner unit problems, and see how to fix them.

1. Your air con unit is unplugged

This is not an issue with your air con as such, but with your electrical connection. So, first and foremost, check that the unit is plugged in! While this might be an obvious issue, on occasion the plug may become partially or completely dislodged. Plugs can easily be knocked out of the wall, so make sure it’s the first thing you check before you start to worry.

How do I fix an air conditioner when it’s unplugged?

Just check that all plugs (depending on your AC model) are correctly connected to their power sockets on your circuit. For more information on how your cooling system is wired, check out the Australian/New Zealand Standard (AS/NZS) 3000-2007, also commonly known as the Wiring Rules, which provide requirements and guidelines for the installation of electrical equipment and appliances, including air conditioners.

2. Your air conditioner won’t turn on

Nothing gets you sweating more than realising your air conditioner won’t turn on at all. This could be the result of a few issues including:

  • A blown fuse or tripped breaker (this can happen if the circuit was overloaded which is common if you tend to leave your AC running for too long)
  • A faulty or clogged condenser fan
  • Loose electrical wiring
  • A faulty thermostat
  • Your air conditioner needs a re-set

How do I fix an air conditioner that won’t turn on?

First things first, go to your electrical panel or fuse box (for older homes) to see if any fuses or mains have blown and turn them back on. If the circuit is fine, double check that the shut-off switch on both the indoor and outdoor is disabled.

After that, you can try resetting your air con to see if there’s an alert, in which case it’s likely a faulty thermostat. Check and replace the batteries. Then set the thermostat’s temperature setting at least five degrees below the current inside temperature so as to not overload the circuit. If the thermostat still doesn’t work, it may need replacement. If your air con is totally non-responsive, it’s likely an electrical issue and you’ll have to call in the experts or an electrician. Don’t attempt to perform wiring repairs yourself.

3. Aircon not blowing cold air

This issue can show up in one of two ways. It could be that your air con is not blowing any air from the duct at all or that the air that’s coming out is not cool. There are multiple reasons this could be happening:

  • A tripped circuit breaker
  • Blocked filter or drain
  • Wrong thermostat settings
  • Low refrigerant levels or leaks
  • Ice build-up

How do I fix an air conditioner that doesn’t blow cool air?

Most of the time, this problem is a breeze to fix. First, check your electrical panel or fuse box for any tripped fuses that reduce your circuit capacity. Then check that your thermostat is set to ‘cool’ and with the right temperature. If nothing seems awry, the next steps are to inspect the unit’s filter and condenser for dust and other residues, and the coils for ice build-up. Check the refrigerant levels too. If nothing seems to work, it may be time to book your air con for a full service and clean. It’s recommended to get your air conditioning system serviced at least once a year.

4. Your air conditioner’s filters or coils are blocked

Blocked filters and coils

Inadequate maintenance can quickly lead to an AC breakdown, and potentially increase your energy bill by causing your unit to work harder. If you leave your filters and air conditioning coils unclean the compressor or fans can fail prematurely, so it’s important to clean filters periodically. Dirty filters and coils can also lead to the most annoying of all air conditioner problems – short cycling. If your air conditioner is stuck in a cycle of turning on, running for a short time, and then turning off again, it’s suffering from short cycling and will benefit from a thorough clean. Washable filters should be cleaned annually to help keep your air con running, but you might like to clean them every three to six months if you find they’re typically covered in a lot of dust and dirt when you take them out. Aim to clean them before peak seasons – summer and winter – to help your air con run efficiently during these times.

How do I fix an air conditioner with blocked filters or coils?

You’ll need to open the front panel of your indoor unit to remove the filters located inside. Give them a good brush and shake, as well as a quick rinse (if you’ve got washable filters) to remove excess dust or dirt trapped. For non-washable filters, you can use a vacuum on low power mode, with an attachment tool to remove blocked dust and other nasties.

To access the fan coil, you’ll need to completely remove the indoor unit’s chassis. Once you’ve gained access to the fan coil, simply spray it with a suitable air conditioner cleaning solution, leave it for a few minutes, and then rinse it off with warm water.

5. The thermostat of your air con is out of place

Room air conditioners are designed with a thermostat sensor (located behind the control panel), which measures the temperature of the air the unit is blowing out. If your unit is not blowing any cold air, the sensor may have been knocked out of position.

How do I fix an air conditioner with a dislodged thermostat?

This will require a technician to adjust it back to the right place. In addition, check the thermostat status on the controller. If it’s set to ‘on’, make sure the thermostat is also set to ‘cool’ (read your manual if in doubt), or you might need to lower the temperature on your controller to help solve this issue.

6. Refrigerant or water leaking

It’s normal to see some condensation on your air conditioner, but excessive moisture can be a sign of leaking water from your unit which is not normal but not uncommon. This would likely be due to a clogged condensate drain line or a broken condensate pump. If the drain line gets clogged with dust, dirt, or mould, water will surge and leak.

However, if you’re seeing coolant lines running along the unit and hearing hissing or bubbling sounds, it could be a sign of damage/cracks to valves and coils that circulate the refrigerant. This is a bit more serious ─ caused by regular wear and tear and a breakdown of components (such as copper pipes, rubber seals, etc.) inside your AC unit, which causes the refrigerant to leak. Refrigerant is the chemical that cycles through your air conditioning system to remove heat from inside your home and release it outdoors.

How do I fix an air conditioner that leaks water or refrigerant?

If leaking water is your issue, you’ll need to unclog your unit’s drain line. You can use a wet and dry vacuum to suck up dust and dirt build-up or whatever the blockage is. If the condensate pump is the issue, you’ll need to replace it. If you’re dealing with a refrigerant leak, DO NOT attempt to fix them yourself as handling refrigerant chemicals can be dangerous due to their toxicity and flammability. Call in the experts for this one.

7. Your air conditioner has blown circuit breakers & fuses

Circuit breakers and fuses

Circuit breakers and fuses are often to blame when the air conditioner stops working. With older homes, it can be common to have circuits that are overloaded if the air con shares a circuit with other appliances such as fridgesmicrowaves, or irons.  Check to see if the fuse has been blown or if the circuit breaker has been tripped. A tripped switch, located in your house’s meter box, can easily be flicked back to the position, but a blown fuse will need replacing.

How do I fix an air conditioner with blown circuit breakers and fuses

If your air conditioner has blown a fuse or the circuit breaker, you’ll need to call on a qualified electrician to fix it. This type of job only takes a couple of hours so it shouldn’t cost you too much in labour, although call-out fees may apply. Do not attempt to undertake any electrical work yourself.

8. Your air con has ice build-up

Ice build-up is the bane of many homes with an air conditioner. If the fan blower belt becomes damaged, ice can form inside the unit, causing a slow cooling performance.  To check if this is the case, switch off the unit and lift the cover to see if there is any ice build-up on or behind the filter.

How do I fix an air conditioner with ice build-up?

The only way to remove ice build-up from your air conditioner is to turn your appliance off and allow time for the ice to completely defrost. The process of defrosting your air con can take anywhere from an hour to over 24 hours, depending on the extent of the ice build-up.

9. Your air conditioner is on the wrong setting

air conditioner settings

Having the right temperature set on your control is key. If your AC is blowing air but still isn’t cold, ensure your unit is set to ‘cooling’ mode on the controller. Typically, this is indicated by a snowflake symbol or the words ‘cold’ or ‘cool’. If it’s already on this mode, check the temperature is low enough for the unit to know it needs to cool. You can test this by dropping the temperature to 16°C on a hot day to check if the air from the air con feels cool before you switch it to an optimum level such as 24°C. This goes for heating as well – if you’re using the air conditioner to heat the home in winter but it’s blowing cold air, check the mode on your controller. Key settings to remember:

  • Snowflake = cooling
  • Sun = heating

During the heating cycle, it’s possible for the unit to blow cold air. This might occur because of the defrost cycle, which switches to a ‘cooling’ mode to allow the outdoor unit to heat up and defrost. However, there might also be settings on the controller that are hindering the fan to switch off – this is where you can consult your manual or a technician. It might also be because some controllers allow you to set the fan motor to constant operation, meaning the fan will operate regardless of settings, defrost cycle, or temperature, which you can switch off.

How do I fix an air conditioner with the wrong settings?

Incorrect settings can be easily fixed by changing the temperature range and cooling mode on the controller directly. If your air con settings look too complicated to change or if you’re not confident about what to do, it may be worth consulting a specialised technician to look over your air conditioner’s settings.

10. Your air conditioner turns on & off continuously

This problem is called short cycling and happens when your AC can’t complete a full cooling cycle and instead starts up in a continuous loop. This causes the compressor to turn on and off more often than usual which can damage it over time. So, what causes your air con to short cycle? There could be a few reasons:

  • Clogged filters restricting airflow
  • Low refrigerant levels
  • Thermostat not calibrated properly
  • Failing compressor
  • Oversized air conditioner unit

How do I fix an air conditioner that turns on & off continuously?

The lowest hanging fruit here is to check that your thermostat is set on the right temperate and cycle. Place it centrally and not too close to vents to ensure you get accurate readings. Next, it’s time to check that your filters aren’t clogged (and give them a good clean) and check that there’s an adequate refrigerant charge. If the problem is that your air conditioner is too powerful for your home, there’s not much you can do but get a replacement. It’s nearly impossible to maintain cooling times if your unit is oversized.

11. Your air con’s compressor is worn out 

Compressor and fan controls can wear out over time, particularly if your unit is constantly getting switched on and off. It’s also common for a compressor to stop working due to a faulty or broken capacitor. An air conditioner can’t work without a functioning compressor, so it will probably need to be replaced. As this is a bit trickier to fix, it’s better to consult with a technician rather than to tackle it yourself.

How do I fix an air conditioner with a worn-out compressor?

The compressor is an expensive part to replace, so depending on how long you’ve had your cooling system for, it may be time to start fresh with a new AC unit rather than pour money into a new compressor for a unit that’s only a few years away from the junk heap. A recent Canstar Blue survey found that consumers typically keep their air conditioner for an average of nine years before replacing it.

Signs of air conditioner problems 

While your air con not properly cooling or heating the room may be a good indicator it’s not working properly, there are a few other signs to look out for to ascertain if your unit is working at full capacity.


How to check your air conditioner is working properly

Are you hearing some strange noises from your air conditioning unit? It could be dirty air filters making it difficult for the AC to process air. Or, it might be that the grille is not fitted properly, which can cause the air to bypass the grille and create a ‘whistling’ noise when the fan is on. Keeping filters clean and centred on the grille should help eliminate these types of noises.

If you’re replacing the grille it’s important to choose the right size for the unit. Undersized return air grilles can make the AC work harder than it should, causing the unit to become noisy. However, if the noise turns into banging or grinding, it’s recommended you switch the unit off immediately. These noises might be caused by a failure in the fan motor or fan motor mounts and will require a technician to fix.

Smoke or steam

If there is steam coming out accompanied by a burning plastic or rubber smell, switch off the unit immediately. In these situations, it is best to call a repair technician. However, there are times when steam isn’t a cause for worry. During winter, it can be common for steam to come from your outdoor unit when it’s set to ‘heating’. This is caused by the defrost cycle which melts and evaporates frozen condensation into the air, which is necessary to ensure it doesn’t turn into an ice box and prevent airflow over the radiator coil.

Water from outdoor unit

Water from outdoor air conditioning unitDuring the heating and cooling cycles, refrigerated air cons are designed to remove moisture from the air. On the heat setting, you might see water on the ground near your outdoor unit. This is condensation, caused by the moisture from the outdoor air meeting the warm coil of the air con and pooling beneath the unit. On the cooling setting, moisture is drawn from the inside air, and in turn, the water is drained out from the roof area into the gutters.

Resetting the unit

If there has been a power failure fault, temperature fault, or no cold air is blowing, you might like to try switching off the power at the fuse box. If you switch it back on, and the problem continues, record the fault shown on the controller (if stated) and provide this information to a specialist.  

You may also be interested in:

Some of the best rated brands of aircon

While any air conditioning unit can have issues along the way, there are some brands that rated highly in Canstar Blue’s Most Satisfied Customer awards that could help you get started if you’re looking for an air conditioner. 

Mitsubishi Air Conditioners

Mitsubishi achieved the most satisfied customer award for 2023 for air conditioners. Mitsubishi’s air conditioners boast features including quiet operation, nano-platinum filters to reduce airborne bacteria and some models also include remote wifi control to adjust aircon temperatures and settings. You can expect to spend from $900 to around $3,000 for a Mitsubishi wall mounted air conditioning unit, with which wattage you need  affecting the price. 

Samsung Air Conditioners

Samsung is known for its high tech appliances and its air conditioners are no different. Including features such as wind free cooling technology and sleep mode, air purification with a tri-care filter to filter dust particles, fibres and animal hair. Retailing from $900 to around $2,500, some Samsung air conditioner models also feature AI smart technology and remote control functionality from your phone. 

Is it time to replace your air conditioner?

Air Con Replacement

If you’ve had a professional check your air conditioner and there’s simply no solution, perhaps it’s time to buy a replacement. In general, air conditioners are claimed to last around nine to 10 years, so it’s worth getting a new AC installed when your unit has reached its twilight years.

These ice boxes are typically energy-intensive, so if your unit has had its day, then it might be worth investing in a new model. New units with high energy efficiency ratings might help reduce running costs and might also provide you with a few extra features for your convenience.

To see which air conditioner brand is the best at helping to keep Australian families cool, follow the link below to our latest ratings report. 

Air Con Reviews & Ratings

Kate King
Casual Content Producer
Kate King produces content for the Home and Lifestyle vertical surrounding appliances and consumer products. She holds a Bachelor of Creative Industries from QUT majoring in Journalism and Media and Communications, and has written for a number of publications over the past five years.

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