You wake up to a 4-8°C Adelaide morning. You grab the remote, flick the air con into heating mode, and wait for that rush of warm air. But you get nothing but cold air hitting you in the face.
When your reverse-cycle air conditioner decides to play up in winter, it’s more than an inconvenience. It can throw off your morning routine, leave staff shivering in an office, or cost you money if your air conditioning unit is working overtime without heating the place.
Most air conditioning systems that do not heat come down to a handful of causes. Some you can fix yourself. Others will need a licensed tech. We’ll walk you through both so you can spot the problem and get it sorted before your toes freeze.
Table of Contents
Why Is My Air Conditioner Not Heating?
When your air conditioning system is blowing cold air instead of hot air, there’s always a reason. Some are quick fixes, others need a licensed technician.
1. Incorrect Thermostat or Operation Settings
Does this sound too simple to you?
Sometimes, the fix is as simple as checking your operation mode.
You’d be surprised how often we find a unit set to the wrong mode.
If your system’s stuck on cooling mode instead of heating mode, you’ll only get cool air, no matter how high you set the thermostat.
Check this first:
On the control panel or remote, choose the heat setting (often marked by a sun icon).
Set the temperature a few degrees above the current air temperature in the room.
Make sure the fan speed isn’t set to “low” if you want quick results.
One customer in Norwood called us, thinking her compressor was shot. We arrived, pressed one button, and the “fault” was fixed. It cost her nothing but a friendly laugh.
2. Dirty Air Filters Choking the System
Dirty air filters and clogged filters are the most common air flow killers.
It’s like trying to breathe through a pillow.
When your air filter is dirty, it blocks the indoor unit from moving air efficiently, which means less warm air comes through.
Your indoor unit can’t move enough air, so it struggles to heat properly.
Here’s what to look for:
Weak airflow from vents.
Dust and lint build up on the filter mesh.
Uneven warmth in the room.
Tip: In Adelaide, especially if you’re near a main road or construction, clean your air filters monthly. At worst, every three months. A blocked filter can make your unit work harder, chew more power, and fail prematurely.
3. Low Refrigerant Levels or a Leak
People come to us, asking why their reverse-cycle air conditioner is not heating. It happens a lot, and here’s what to know:
Your reverse-cycle air conditioner uses refrigerant gas to shift heat between the indoor unit and the outdoor unit. If there’s not enough in the system, you’ll get blowing cold air even in heating mode.
When your reverse cycle air conditioner is not heating, you’ll see signs like:
• Hissing or bubbling sounds from the outdoor unit.
• Ice builds up on pipes or coils.
• Slow heating or no heating at all.
If there’s a refrigerant leak, you can’t top this up yourself. It’s illegal in Australia without the right licence. An REQ Refrigeration and Air Conditioning technician can fix the leak for you and then recharge the gas.
4. Broken Parts Inside the Unit
If the broken thermostat isn’t telling the system to heat, or the fan motor is dead, your air conditioning unit won’t push hot air at all.
Other parts can fail too. These include the:
• Compressor (the “heart” of the system).
• Heating element (in some models).
• Electrical boards or sensors.
We’ve received quite a few calls from homeowners because their systems kept tripping the circuit breakers. In one case, ants had nested inside the outdoor unit control board. After the repair, we recommended a pest control plan, and that was it!
5. Reverse Cycle Aircon Not Heating Because of the Reversing Valve
The reversing valve enables your system to perform both heating and cooling functions. If it gets stuck, you’ll have cool air no matter what mode you pick.
Other causes can be:
• Tripped circuit breaker, cutting power to the heating side.
• Faulty defrost mode that won’t clear ice off the outdoor unit.
If you hear the unit trying to start but no warm air comes out, this could be the issue. It’s not a DIY job; a tech will need to test and replace the valve.
6. Outdoor Conditions Throwing It Off
Here in Adelaide, early frosts can cause ice buildup on the outdoor unit. Usually, the defrost cycle kicks in and melts it. If that cycle fails, your unit stays cold.
You might also see poor heating if:
• The outdoor unit is blocked by leaves or dirt.
• There’s poor ventilation around the unit.
• The power supply is unstable.
Quick tip: Always keep the area around your outdoor unit clear by at least 30cm on all sides.
Fix Air Conditioning Heating Issues With REQ Refrigeration
Once you’ve checked the basics, it’s time to call in an expert. REQ Refrigeration and Air Conditioning is proudly SA-owned with decades of experience handling Adelaide’s heating and cooling challenges.
Fast, Professional Repairs
When your air conditioning unit is blowing cold air in the middle of winter, speed matters. REQ’s technicians provide same-day and emergency callouts for heating faults so you can stay warm without long waits.
Skilled Technicians for All Brands
From a small split system to a large ducted reverse cycle air conditioner that’s not heating, our team is trained on all major brands, including Daikin, Mitsubishi Electric, and Fujitsu. We quickly diagnose faults like a broken thermostat, damaged reversing valve, or refrigerant leaks.
Preventive Maintenance Saves Money
Regularly serviced systems are far less likely to fail prematurely. REQ offers maintenance plans that include:
• Cleaning air filters and coils.
• Checking refrigerant levels.
• Inspecting the outdoor unit for ice buildup or water leaks.
Preventive care is cheaper than emergency repairs and keeps your air conditioning system working year-round.
Frequently Asked Questions
Why is my aircon not heating properly?
Nine times out of ten, it comes down to a handful of issues. Sometimes it’s as simple as the system being stuck in cooling mode instead of heating. Other times, the air filters are clogged with dust and pet hair, which can choke the airflow by almost half. Low refrigerant gas is another common one; if there’s not enough in the system, your unit can’t move heat around properly, so you’re stuck with cold air. And then there are the bigger faults, like a broken thermostat or a fan motor that’s given up.
What should I do if my reverse cycle aircon isn’t heating?
First thing, grab the remote and make sure it’s actually on heating mode. Then check that the set temperature is a few degrees higher than the room temperature, if it’s 16°C inside, aim for 20°C or 21°C. Give the filters a good clean while you’re at it. If your circuit breaker has tripped, reset it and see if that brings the system back. Also, take a quick look at the outdoor unit and clear away leaves, dirt or spider webs that might be blocking it. If you’ve tried all that and it’s still blowing cold air, call us to check things like the reversing valve or gas levels.
How long does it take to repair an aircon that isn’t heating?
It depends on what’s wrong. If it’s something small, like a dirty filter or incorrect settings, you can have it sorted in under half an hour. If we’re topping up gas after fixing a small leak, you’re looking at about one to two hours. Bigger jobs like replacing a reversing valve take longer, usually half a day, especially if we need to run full system tests afterwards.
Can I fix my aircon heating issue myself?
There are a few things you can safely do yourself. You can check the settings, clean the filters every month or two, and ensure there’s at least 30 centimetres of space around the outdoor unit for proper ventilation. What you shouldn’t do is try to handle refrigerant gas or start pulling the unit apart. In Australia, you need an ARC licence to work on refrigeration systems.
Do you offer repairs for all types of air conditioners?
Yes. We work on everything from small wall-mounted split systems in units and family homes to full ducted reverse cycle setups in larger houses and commercial spaces. That includes rooftop packaged systems and cassette units you’ll find in shops or offices. We service and repair all the big brands you’d see in Australia, from Daikin to Mitsubishi Electric, Fujitsu, Panasonic, Samsung, LG, and plenty more. If it heats or cools, chances are we’ve worked on it before.
Don’t Let a Faulty Aircon Ruin Your Winter
If your reverse cycle aircon is not heating, it’s turning winter into an endurance test. Don’t wait for it to get worse. The longer it struggles, the more strain you put on the system and your power bill.
REQ Refrigeration and Air Conditioning has been keeping Adelaide homes and businesses warm for decades at affordable rates with no-nonsense advice and quality work every time.
Call us on 1800 202 073 or request a consultation online.
