Air Con Stopped Working? Stay Cool With These 5 Checks

When your air conditioning unit stops working right before the summer heat sets in, it’s stressful. Rising temperatures, stuffy rooms, and no airflow is the last thing you want as we head into hotter weather!

The good news is that many common air conditioning issues have simple, safe checks you can do yourself before calling in a technician.

Below, we break down the most common reasons your air conditioner stops working, what causes them, and how to troubleshoot each issue step by step. This guide is written for homeowners who want clear, practical advice without the technical jargon.

1. Air Con Not Turning On

If your system won’t start at all, the problem is usually electrical, thermostat-related, or linked to the power supply.

Possible causes

• No power reaching the indoor or outdoor unit
• Incorrect thermostat settings
• Tripped circuit breaker or blown fuse

What you can check

• Make sure the air con is plugged in and switched on at the wall
• Set the thermostat to Cool or Auto, and drop the temperature lower than the room temperature
• Check your switchboard for a tripped circuit, turn it off and back on
• Replace blown fuses if your system uses them

If the system still won’t switch on, contact us so one of our expert technicians can check it properly.

2. Air Con Running But Not Cooling

Your air con may be working, but still not cooling the room properly. This is one of the most common complaints during summer.

Possible causes

• Dirty or clogged filters
• Blocked or closed vents
• Debris around the outdoor unit is restricting airflow

What you can check

• Clean or replace the air filter regularly to maintain airflow
• Make sure vents and registers aren’t blocked by furniture or curtains
• Clear leaves, dirt, and debris from around the outdoor unit and condenser coils

Airflow problems are a common cause of cooling issues and can often be resolved with simple maintenance.

3. Air Con Blowing Warm Air

If your system is blowing warm air instead of cooling, the issue could be incorrect temperature settings, low refrigerant levels, or a compressor problem.

Possible causes

• Thermostat set incorrectly
• Low refrigerant levels
• Compressor faults
• Leaks or restrictions in ductwork

What you can check

• Double-check that the thermostat is set to cool mode
• If you suspect refrigerant is low, do not try to fix this yourself
• Look for obvious damage or disconnected ductwork around accessible areas
• If the thermostat is faulty, consider replacing it

Only a licensed technician should handle refrigerant repairs, so if you think this might be the issue, get in touch with us, and we’ll help.

4. Strange Noises Coming From the Air Con

Your air con should run smoothly. New or unusual sounds often mean something is loose or worn out.

Possible causes

• Loose or damaged screws, bolts, or fan blades
• Poor lubrication
• Motor or fan issues

What you can check

Listen for the type of sound:

• Rattling often means loose parts
• Grinding can indicate metal-on-metal contact
• Buzzing can point to electrical issues
• Tighten visible loose screws carefully
• If noises continue, stop using the system until a technician inspects it

Catching unusual sounds early can save you stress later on. Give us a call, and we’ll make sure everything’s running properly!

5. Air Con Leaking Water

A leaking air con doesn’t always mean something serious, but it shouldn’t be ignored.

Possible causes

• Blocked condensate drain line
• Full or dirty drain pan
• Dirt buildup on coils or filters causing excess condensation

What you can check

• Clear the condensate drain line using a wet-dry vacuum or a flexible brush
• Empty and clean the drain pan
• Replace dirty air filters
• If the evaporator coil is dirty, book a professional clean

Water leaks can cause mould and damage around the unit, so it is best to address them assoon as possible.

When Your Air Con Needs More Than a Quick Fix

DIY checks are a good place to start, but some air con issues need a licensed technician to diagnose them safely. If you notice any of the following, it’s time to call a professional:

• The unit still won’t turn on after basic checks
• Cooling is weak or inconsistent even with clean filters
• Your switchboard keeps tripping when the air con runs
• You notice burning smells or electrical buzzing
• There are ongoing leaks or loud noises coming from the unit
• Warm air continues blowing despite correct thermostat settings

These signs often point to deeper issues like compressor faults, electrical problems, refrigerant leaks, or blocked internal components — all of which require a trained technician.

With over twenty years of experience, Roberts Air Conditioning provides reliable air conditioning services, repairs, and installations across Sydney. We diagnose faults quickly, explain your options clearly, and help get your home cool and comfortable again before the summer heat arrives.

Need help with an air conditioning system that stopped working? Contact us today for fast, reliable service.

‍