If your air conditioner is running but not cooling, the most common fixes are: check the thermostat is set to “cool”, clean the air filters, and clear debris from around the outdoor unit. These three checks resolve most cooling problems. If the unit is still blowing warm air, icing up, or leaking after that, it usually means low refrigerant or a compressor fault — which needs a licensed technician. Here is how to troubleshoot it step by step.
Quick Troubleshooting Checks (Do These First)
1. Check the Thermostat Settings
Make sure the unit is set to “cool” mode, not “fan” or “heat”, and that the target temperature is set a few degrees below the current room temperature. It sounds obvious, but a wrong mode setting is the single most common cause of an air conditioner that runs but doesn’t cool.
2. Clean or Replace the Air Filters
Dirty filters are the number-one cause of weak cooling. They restrict airflow, ice up the coil, and force the system to work harder for less result. Slide out the indoor filters, wash them under water, let them dry fully and refit. Do this every 4 to 6 weeks during heavy summer use.
3. Check the Outdoor Condenser Unit
Head outside and check the outdoor unit is running and clear. Remove leaves, grass clippings and debris from around it, and make sure nothing is blocking airflow to the fins. A choked outdoor unit can’t dump heat, so the system can’t cool the room.
4. Close Doors and Windows
Cooling an open house is a losing battle, especially in a Brisbane summer. Close external doors and windows in the room you’re cooling so the unit isn’t fighting incoming heat.
When to Call a Professional
If you’ve worked through the checks above and the unit still won’t cool, the problem is beyond a DIY fix. Turn the unit off and call a licensed technician if you notice any of these:
- Blowing warm air after the thermostat and filters are confirmed correct — usually low or leaking refrigerant
- Ice forming on the indoor coil or pipes — an airflow or refrigerant fault
- Water leaking from the indoor unit — a blocked drain line
- Tripping the circuit breaker — an electrical fault that needs a licensed electrician
- Grinding, buzzing or rattling noises — a failing fan motor or compressor
- Burning or electrical smells — switch it off at the wall immediately and call a professional
In Australia, refrigerant handling and electrical work must legally be carried out by a licensed technician. Connex Electrical holds both an electrical contractor licence (QLD #92217) and an ARC refrigeration licence (#AU42842), so we can diagnose and fix the full range of cooling faults — electrical and refrigeration — in one visit.
What Does It Cost to Fix?
| Job | Typical Cost |
|---|---|
| Callout & diagnosis | From $88 |
| Labour (in-visit repairs) | $185/hr |
| Split system service & clean | $120 – $250 |
| Refrigerant regas / compressor work | Quoted after diagnosis |
Most airflow-related cooling problems are solved by a professional air conditioning service, which clears filters, coils and drains and gets the system cooling properly again. If a repair is needed, we quote it upfront before any work starts.
Air Conditioning Service & Repair Across North Brisbane
Connex Electrical provides air conditioning service and repair for all brands across Brisbane and North Brisbane. Whether it’s a quick filter clean, a refrigerant fault or a full diagnostic, our licensed team gets your system cooling again fast. We also handle new air conditioning installation if your old unit is past saving — see our guide on installation costs and how often you should service your air conditioner.
Reviewed by Lee Gundenswager (Lead Electrician, Connex Lic #92217) and Darren Standring (Owner).
Frequently Asked Questions
The most common reasons are a dirty air filter restricting airflow, incorrect thermostat settings (set to fan instead of cool), a blocked or dirty outdoor condenser unit, or low refrigerant. Start by checking the thermostat and cleaning the filters — these fix the majority of “running but not cooling” cases. If it still won’t cool, the refrigerant or compressor may need a licensed technician.
First, set the thermostat to “cool” and a few degrees below room temperature. Second, clean or replace the air filters. Third, clear leaves and debris from around the outdoor unit and check it is running. Fourth, make sure doors and windows are closed. If none of these restore cooling, the issue is likely refrigerant, electrical or the compressor — which needs a licensed air conditioning technician.
Warm air usually means low or leaking refrigerant, a frozen evaporator coil, or a faulty compressor. It can also be a thermostat set to “heat” or “fan” by mistake. Check the mode first, then the filters. If it is still blowing warm, switch the unit off and call a technician — running it low on refrigerant can damage the compressor.
Ice on the indoor coil or pipes is usually caused by restricted airflow (dirty filters), low refrigerant, or a faulty fan. Turn the unit off and let the ice melt fully before running it again. Because icing often signals a refrigerant or airflow fault, it should be inspected by a licensed technician to prevent compressor damage.
A standard callout and diagnosis starts from $88. Many cooling faults — filter cleans, thermostat issues, drainage and electrical checks — are resolved in a single visit at $185 per hour. A full split system service and clean, which fixes most airflow-related cooling problems, costs $120 to $250. Refrigerant regas or compressor work is quoted after diagnosis.
Call a licensed professional if the unit is blowing warm air after you’ve checked the thermostat and filters, if it is icing up, leaking water, tripping the circuit breaker, making grinding or buzzing noises, or if you smell burning or electrical odours. Refrigerant and electrical work must legally be done by a licensed technician in Australia.
Air conditioner still not cooling? Call Connex Electrical on 0474 207 609 or visit our contact page to book a licensed technician across Brisbane and North Brisbane.