Why isn't my air conditioner turning on?

Three essentials for a sweltering Aussie summer include thongs, boardies (or a bikini) and a working air conditioner. So what do you do when - all of a sudden - your aircon won’t power up? No matter how many times you jab at the "on" button, absolutely nothing happens.

The situation is far from ideal, but it's one that many Australians commonly find themselves in all the time. Sometimes, an air conditioner system that worked completely fine yesterday won’t even turn on the following day.

The good news is, the problem may be something simple that you can fix yourself. So, before grabbing your phone and frantically calling the closest air conditioning technician with the hope of restoring that icy cold breeze ASAP, have a read of our guide.

We’ve compiled some common reasons that your air conditioner may not be switching on, and how to solve them.

Possible Cause: Tripped Circuit Breaker

If a once-off tripped air conditioner circuit breaker is the reason that your air conditioning won’t switch on, then you’re in luck. This is a very straightforward problem with the solution being as easy as simply flicking a switch. It’s normal for a circuit breaker to switch off from a power surge in severe weather conditions, like after a storm.

However, if your air conditioner unit is causing your circuit breaker to continuously switch off, then you may be looking at a more serious problem.

A circuit breaker trips when an air conditioners system is using more amps than the breaker is rated for. A circuit breaker that continually switches off could indicate a variety of different problems with your air conditioner.

This problem could range from a dirty air filter or a dirty outside unit, to an issue with the breaker itself, a shorted motor or a faulty compressor.

How to solve:

Head over to your circuit box and check if the switch connected to your AC system has flicked off. If this is the first time this has happened, simply flick the switch back on and - in an ideal situation - your air conditioner should work again without an issue.

If the switch continues to flick off, then there is a bigger issue at hand. You can try changing the air conditioner filter, but for other issues, it’s better to call in a technician from an air conditioning company. A technician can identify exactly what’s wrong with the system and address that problem specifically.

Possible Cause: Shut-off Switch is Engaged

Most air conditioners have a shut-off switch located near the outdoor part of the unit. The switch is usually inside a metal box that will be mounted on the wall. If you’ve recently had some work done on your unit, a technician may have switched the safety switch on while they were doing the repair and forgotten to turn it back off.

How to solve

Thankfully, there is a very simple solution. Just open up the box and identify the “on” and “off” button. Pull the plug out of the “off” box and pop it into the “on” box. If your Safety switch was set to “off” and you set it “on”, but the unit still doesn’t work then there’s another problem with your system.

Possible Cause: AC Float Switch is Engaged

An AC float switch is located in the condensate drain line of many air conditioners. Its purpose is to turn the unit off when water begins to accumulate in the drain line. So, if a safety switch is engaged, there’s a good chance you’ve got a drainage problem, specifically in the condensate drain line.

Repairing water damage in an air conditioner can be expensive, so a safety switch is a great way to be notified of the water problem before it causes damage. If your unit doesn’t already have a float switch, it’s a smart idea to have one installed. The devices are simple and cheap and can save you from significant flooding damage, as well as clogged pipes.

How to solve:

In this situation, it’s the safety switch that’s prevented your air-conditioning from working. We can’t stress enough how important it is not to remove the safety switch and continue to run your unit, as water damage can almost be guaranteed.

The best solution for a switched AC float is to notify a technician who can identify where the blockage is and why it’s happening, and then clear it out.

Possible Cause: Aircon Needs to be Reset

If your AC unit is blowing warm air, or just not responding at all, you can try resetting your air conditioner. Like how Apple technicians constantly recommend a restart when you have a problem with your iPhone or MacBook - an AC reset could be an easy solution to your frustrating problem.

Sometimes an AC system may not fully kick on after a power outage and a reset can help it power up again.

How to solve:

Different models have reset buttons in different positions, but almost all units should have one. These buttons are usually small and red and your AC’s manual should have information about where it is located.

Before hitting the little red button, make sure you unplug your unit from the wall for at least 30 seconds and then plugged it back in. This will also help with powering your unit up again. Once the unit is plugged back in try the reset button for three seconds and then release. Hopefully, your air conditioner will have kicked back on by this point!

If your unit doesn’t have a reset button you can try and reset it manually. To do this shut off the power to the compressor unit. Next, flip the switch off in your breaker box that is connected to the AC unit. Then, unplug the unit from the power supply and leave it for 30 minutes. After 30 minutes you can plug your unit back in and it will have been manually reset.

Possible Cause: Faulty Thermostat

A faulty thermostat could be the reason that your air conditioner isn’t responding. The thermostat is the main control that talks to the unit to tell it when to start and when to shut down.

If the thermostat screen is blank when you try and power it up, then you can probably assume that the problem is related to the thermostat specifically. However, if the screen still powers on and looks normal, the problem could still be related to the thermostat being faulty.

How to solve:

There could be a variety of reasons behind the fault with your thermostat. If the thermostat is battery powered, try switching out the batteries.

A common mistake with a thermostat is accidentally having the thermostat set to “heat” instead of cool. When set to heat your air conditioner won’t turn on no matter what, so change the mode. You can also try setting the temperature to the lowest possible degrees setting, this may power it back up.

If none of the above solutions work, there may be a deeper issue with your thermostat and it may even need to be replaced. To diagnose this you should call a technician from an air conditioning company who will be able to figure out what the problem is.

Possible Cause: Frozen Evaporator Coil

A frozen evaporator coil can be the culprit for the reason your air conditioner isn’t working. If your air conditioner powers on but you feel hot air, or no air at all, then a frozen coil could be the root of the problem.

You can easily check if you have a frozen coil by having a look at your unit and seeing if a layer of ice has developed. Unlike condenser coils, which are located on your outdoor unit, evaporator coils are located on your furnace. If you can see ice, then a frozen evaporator coil is likely the problem.

This problem is important to address immediately as a frozen over coil can damage a compressor, which is an expensive fix.

How to solve:

As mentioned above, you can identify whether freezing over is the problem by looking for ice on the unit. If you’ve identified this as your problem, you’ll still need to know exactly what’s causing the unit to freeze.

Evaporator coils usually freeze because of restricted airflow. This could be due to something as simple as a dirty air filter, or something more sinister. There are a variety of reasons that the air flow has been reduced. A technician can identify the problem and restore the airflow.

Possible Cause: Locked Air-con Control

If your air conditioner is a wall-mounted unit and uses a remote control, then the lock feature may have been accidentally engaged. If this has happened, then your air conditioning unit won’t respond when you try and power it up as the remote is locked to stay in its current setting, which is off.

It’s easy to recognise if this is your problem. Simply check the digital screen of your remote when you hit the "on" button. If a lock icon periodically flashes up, then it’s safe to say you’ve found the issue.

How to solve:

Different air conditioning units and brands have different commands and buttons. Usually, if you hold either the plus (+) and minus (-) buttons, or the higher degree and lower degree buttons, at the same time then it should disengage the lock feature. However, as the commands range it’s best to check your manual to find out how to exit the lock feature.

Possible Cause: Blown Fuse

A blown fuse can be the reason your air conditioning system isn’t responding. A fuse will actually blow as a safety measure, this happens to protect against further damage to your AC unit.

Fuses can blow for a variety of reasons, but one of the most common causes of a blown fuse is when your air conditioning system gets too hot. This often happens when an AC unit is left running for a very long period of time in very hot conditions.

However, this isn’t the only reason for a fuse blowing. A faulty condenser fan, dirty filter, loose electrical connections or a leak can all also be the reasons behind the blown fuse.

How to solve:

Replacing a fuse can be technical as the right fuse needs to be selected and installed properly. Plus, if there’s a bigger reason behind why your fuse blew, then the same thing will happen again.

A fuse blow can be a helpful warning sign of a bigger problem before serious damage is done. For this reason, it’s best to call a technician to identify the source of the problem and replace the fuse.


How do I reset my AC unit?

Most modern AC units should have a red reset button located somewhere on the unit. To quickly find out where this button is located, consult your manual.

If your unit doesn't have a reset button, you can also trigger a manual reset. Do this by following these simple steps:

  1. Power down your air conditioner unit
  2. Locate the switch on your breaker board that's connected with your air conditioner and switch it "off" (or you can simply switch everything off)
  3. Wait for thirty minutes before switching the breaker switch back on.
  4. Power up your air conditioner and see if it works!

Can a blown fuse cause air conditioners not to work?

A blown fuse is a common cause behind a non-responsive air conditioner. However, a fuse that has blown is usually a symptom of a bigger problem.

It's important to get to the root of the problem and find out why the fuse blew in the first place so that you can identify what needs to be repaired.

Unfortunately, a fuse that has blown could indicate a number of different problems, from a faulty condenser fan to loose electrical connections and more.

Time to call the experts?

If you are still having issues - it's time to call in the experts. Our Brisbane-based air conditioning repairs team are on hand to give you the assistance you need. Call us on 07 3283 5566 or fill out a quick quote to get your air conditioner back up and running!

Experiencing other air conditioner issues?

Check out our other guides on common problems below:

My air conditioner heat mode is not working

My air conditioner will not turn off

My air conditioner is making a loud buzzing noise

My air conditioner is sweating inside

My air conditioner is icing up

My air conditioner is blowing hot air

My air conditioner is leaking water

My air conditioner smells bad

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