If your reverse cycle air conditioner isn’t blowing warm air when you need it most, don’t worry – you’re not alone.
While these systems are designed to keep your home comfortable year-round, sometimes things don’t go as planned. Instead of heating, your unit might be pushing out cool air or doing nothing at all.
The good news is, in many cases, the problem is something simple that you can check yourself before calling in a professional.
From incorrect thermostat settings to clogged filters or outdoor unit issues, there are a few common reasons why your system might not be heating properly.
In this blog, we’ll walk you through five likely causes of a reverse cycle AC not heating – and what you can do about them – so you can get your home warm and cosy again without too much fuss.
1. Incorrect Thermostat Settings
Sometimes the reason your reverse cycle air conditioner isn’t heating is as simple as the thermostat being set incorrectly. Before you assume something’s broken, check the following:
- Mode setting – Make sure your system is actually set to heating (often displayed as “heat” or a sun symbol) and not cooling or auto.
- Temperature setting – Set the thermostat a few degrees higher than the current room temperature. If it’s too close, the system might not activate.
- Fan setting – If the fan is set to “on” instead of “auto,” it might blow air even when the unit isn’t heating, giving the illusion that it’s not working.
- Timer or schedule settings – A pre-set timer could be preventing the system from running when you want it to.
- Remote batteries – Weak batteries can cause your remote to send incomplete signals, which may lead to the wrong mode being selected.
Adjusting these settings can often resolve the issue without needing professional help. Always start here – it might save you time and money.
2. Dirty or Clogged Filters
One of the most common reasons your reverse cycle air conditioner isn’t heating properly is dirty or clogged filters.
Over time, dust, pet hair and other debris can build up in the filters, restricting airflow and making it harder for your system to push warm air into your home. When airflow is blocked, the unit has to work much harder, and it may struggle to heat at all.
The good news is that this is an easy fix. Simply open the indoor unit, remove the filters, and give them a thorough clean. Rinse them with lukewarm water and let them dry completely before reinstalling. If the filters are damaged or extremely worn, it might be time to replace them.
Cleaning your filters every few months – more often if you have pets or allergies – can improve your system’s performance and energy efficiency.
Not only will this help your aircon heat your space more effectively, but it’ll also extend the life of the unit and help maintain better indoor air quality.
3. Low Refrigerant Levels
Refrigerant is a crucial part of how your reverse cycle air conditioner heats your home. If the system is low on refrigerant, it can’t absorb and transfer heat properly, which means you’ll likely notice cold air instead of warmth.
Here’s what to look for:
- Weak airflow or cold air – If your unit is in heating mode but still blowing cold or lukewarm air, refrigerant could be the issue.
- Longer heating times – It takes noticeably longer for your home to warm up.
- Hissing or bubbling noises – These could indicate a refrigerant leak somewhere in the system.
- Ice on the coils – Ice buildup on either the indoor or outdoor unit is another red flag.
Low refrigerant levels aren’t something you can fix yourself – it’s a job for a licensed heating, ventilation and air conditioning (HVAC) technician. They’ll need to find and repair any leaks before recharging the system with the correct type and amount of refrigerant.
If you suspect low refrigerant, it’s best to switch off the unit and call in a professional to avoid damaging the system further.
4. Outdoor Unit Issues
If your reverse cycle air conditioner isn’t heating, don’t forget to check the outdoor unit – it plays a vital role in the heating process. When in heating mode, the outdoor unit pulls heat from the outside air and transfers it indoors. But if it’s blocked, dirty or iced over, it can’t do its job properly.
Leaves, dirt, and debris around the outdoor unit can restrict airflow and reduce efficiency. In colder months, frost or ice buildup can also prevent it from working.
Some units have a defrost mode that automatically clears ice, but if this function isn’t working or the ice buildup is too severe, the system may shut down or blow cold air instead.
Start by turning off the system and clearing any visible debris. Check for ice buildup and gently remove it if safe to do so. Never use sharp tools or pour hot water – just let it defrost naturally. If issues persist, it might be time to call in a technician to inspect the coils, fan or defrost controls.
5. Malfunctioning Reversing Valve
The reversing valve is what allows your reverse cycle air conditioner to switch between heating and cooling modes. If this valve isn’t working properly, your system might get stuck in cooling mode – even if you’ve selected heating on the remote.
Here are some signs to look out for:
- Blowing cold air in heating mode – The most obvious sign that the reversing valve isn’t doing its job.
- No noticeable change when switching modes – If you change from heating to cooling (or vice versa) and nothing happens, the valve could be stuck.
- Unusual noises – Clicking, hissing or buzzing sounds when switching modes can indicate a valve issue.
- Inconsistent performance – Your system may heat intermittently or struggle to maintain a consistent temperature.
Unfortunately, a faulty reversing valve isn’t a DIY fix – it requires diagnosis and repair by a licensed HVAC technician. If your unit is fairly new, this could be covered under warranty.
If the system refuses to heat and none of the basic settings seem off, it’s time to have a professional check the reversing valve.
Be Prepared for Winter’s Chill
When your reverse cycle air conditioner isn’t heating, it’s easy to assume the worst – but often, the fix is simpler than you think.
Whether it’s something minor like incorrect settings or dirty filters, or more technical like low refrigerant or a faulty reversing valve, identifying the issue early can save you time, money, and discomfort.
Start with the basics and work your way up – many problems can be sorted with a quick clean or a settings adjustment. But if the issue persists, don’t hesitate to call in a licensed technician to get your system back in top shape.
A well-maintained air conditioner not only keeps your home warm and cosy but also runs more efficiently and lasts longer. Stay warm and don’t let the cold win.
Please note: This information is provided for advice purposes only. Regulations differ from state to state, so please consult your local authorities or an industry professional before proceeding with any work. See our Terms & Conditions here.
FAQs About Faulty Reverse Cycle ACs
Do you have any questions about your reverse cycle air conditioner not heating? Keep reading for answers to some of the most commonly asked questions.
This usually means the system is stuck in cooling mode. It could be something as simple as incorrect settings or something more technical like a malfunctioning reversing valve. Double-check the thermostat first, and if everything looks right, it might be time to call a technician.
For best performance, clean your filters every 2-3 months. If you have pets, allergies, or live in a dusty area, monthly cleaning is even better. Clean filters help your system heat efficiently and keep your air quality in check.
You can handle some basic maintenance tasks, like cleaning filters or checking the thermostat settings. But if the problem involves refrigerant, electrical components, or internal parts like the reversing valve, it’s safest to call a licensed HVAC technician.
