5 Reasons Why Your Reverse Cycle Air Conditioner Isn’t Heating Well

Ever find yourself in a situation where your reverse cycle air conditioner’s heating mode isn’t working well? When this happens, your air conditioner might be blowing out cold air instead of warm. 

In this article, we’ve compiled the most common reasons why your reverse cycle air conditioner might not be heating your space properly. Read on to find out what they are and what you can do to fix them.

AC Needs To Be Serviced 

We’ve said this before and we’ll say it again – the number one reason for an ineffective air con is its lack of service. Air conditioners need to be serviced on a yearly basis to prevent it from deteriorating faster than it should. 

Once your air conditioner hits the 3 year mark, its efficiency will drop by as much as 15%. Making sure you keep to the yearly servicing schedule will help make up for this loss in efficiency

A service usually includes checking to see if all parts are functioning properly and if the settings are accurate. Air filters, coils and other crucial parts are thoroughly cleaned or replaced if needed. If any parts are malfunctioning, they are fixed or replaced accordingly. Lastly, the airflow is tested to see if the air conditioner is running properly. 

AC Is Past Its Lifespan

The 2 most common types of air conditioners that provide heating in Australia are split systems and ducted air conditioning. 

Just like with humans, the age of the air conditioning system is directly proportional to its efficiency. You’ll find that older units lose their efficiency after a while, typically past the 3 year mark. 

Most air conditioning systems last anywhere between 10 – 20 years and once it’s past this stage, it would be more economical for you to replace your unit instead of getting it routinely serviced. Most warranties would cover repairs and replacements of up to 10 years.

Incorrect AC Size For Room

When you’re deciding on getting an air conditioner for your home or a specific room in your home, size matters. The larger the space, the more power you’ll need to sufficiently heat the space. Use the chart below to check if you have the right AC capacity for your area. 

Room Size Description Estimated Capacity
Small (up to 20m2) Small kitchen, bedroom, study 2 – 2.5kW
Medium (20 – 40m2) Small lounge, bedroom with adjoining bathroom 2.5 – 5kW
Large (40 – 60m2) Mid-sized lounge, large bedroom or kitchen  4 – 6kW
Extra large (60+m2) Large lounges, open-plan areas 5 – 9kW

Broken Thermostat

Another common reason why your air conditioner isn’t functioning properly could be due to a broken thermostat. Specifically, if you’re experiencing difficulty changing system controls or setting the temperature.


How To Test For This

Firstly, try testing it out to see if it really is broken. Check the temperature that you’ve set it on and try turning it up a notch to see if you notice any change in temperature. It’s a simple check but it’s the best way to see if a broken thermostat really is the culprit in this case. 

What To Do If Its Broken

If you’re using a digital thermostat, the simple fix would be to just replace its batteries. If this still doesn’t do the trick, try resetting it to the manufacturer’s settings. If it still isn’t working after all that, check if there’s a tripped circuit in your switchboard.

If all else still fails, reach out to a trained technician to help you diagnose the problem and resolve it. 

Clogged Filters

Another reason why your air conditioner isn’t functioning at its best might be a clogged filter. Air filters should be replaced at least once a year to ensure that the air flowing through the air conditioning system remains filtered

Block air filters can cause other components in the air conditioner to fail prematurely, causing it to not heat properly. 

Can Be Cleaned Independently

The good news is that cleaning your air filters is fairly easy and can be done by almost anyone. It’s just a matter of removing the air filters from the air conditioner and wiping them clean or rinsing them under running water. 

If you prefer to go for a deeper clean, you can also clean it down with a soap solution. 

Other Possible Reasons

Ice Build Up

This happens when the outdoor system is exposed to very cold air during winter months. While the indoor unit is working to heat the place, the outdoor unit stays in the cold perhaps from poor ventilation or due to its age. This is when ice buildup can occur.

If this happens, it can expand and even break or damage some parts of the air conditioner. To resolve this problem, you’ll need to shut off the unit and let the ice thaw for a few hours. Whatever you do, don’t start hacking at the ice as that can damage the air conditioning unit. 

Once the ice has thawed, check your air filter and other key components of your air conditioning unit. Changing your air filter frequently will keep clogs from forming. 


Mould could be growing in your system and getting in the way of it functioning properly. This is because it can cause blockages in your unit and disrupt the airflow. 

To avoid mould building up, change your air filters frequently – every 1-3 months. Also, get your ducts checked and cleaned by a professional once every few years

Compressor Issues

A malfunctioning compressor could be the cause of your air conditioner not heating properly. This is the part of the aircon that changes the refrigerant from a cool, low pressure liquid to a hot, high pressure gas. 

If you’re servicing your air conditioning unit on schedule, a faulty compressor shouldn’t be an issue as they can last up to 10-15 years. But if you think your compressor isn’t working well, you’ll need to have a trained professional look at it as the refrigerant gas can be harmful and requires technical handling.

Stay Warm This Winter

As we’ve seen, there could be multiple reasons why your air conditioner isn’t heating well.

If you’ve gone through our checklist and are still facing issues with heating, reach out to our trained technicians to book an appointment and get them resolved. 

Keep calm and stay warm!