Step 1: Check Your Thermostat and Remote
Before assuming the worst, start with the basics. Check that your thermostat or remote control is set to cooling mode (not heating or fan-only), the temperature is set below the current room temperature, and the batteries in the remote are not dead. It sounds obvious, but a surprising number of emergency callouts turn out to be a thermostat set incorrectly or a remote with flat batteries. If you have a wall-mounted controller, check that it is displaying properly and has not lost power. On some systems, a power interruption resets the thermostat to default settings.
- •Ensure the unit is set to COOL mode, not HEAT or FAN
- •Set the temperature at least 2–3 degrees below room temperature
- •Replace remote batteries if the display is faint or unresponsive
- •Check the wall controller is powered and showing correct settings
- •Try turning the system off for 30 seconds, then back on
Step 2: Check the Circuit Breaker and Isolator Switch
Air conditioners in Brisbane homes are typically on a dedicated circuit. Go to your switchboard and check if the circuit breaker for the AC has tripped. If it has, switch it back on and see if the AC starts. If it trips again immediately, do not keep resetting it — there is an electrical fault that needs a professional. Also check the isolator switch, which is a small switch usually located on the wall near the outdoor unit. This can sometimes be accidentally switched off during garden maintenance or by children. The indoor unit will not work if the outdoor unit has no power.
- •Check the switchboard for a tripped AC circuit breaker
- •Reset once — if it trips again, call a technician
- •Check the isolator switch near the outdoor unit
- •Ensure both indoor and outdoor units have power
- •Check if a general power issue is affecting other appliances too
Step 3: Clean or Replace the Air Filters
Dirty air filters are the single most common cause of AC problems, and the easiest to fix yourself. When filters are clogged with dust, the unit cannot draw enough air, causing it to overheat, freeze up, or shut down on a safety cutout. On a split system, open the front panel of the indoor unit and slide out the filters. Wash them under running water, let them dry, and reinsert. On ducted systems, check the return air grille (usually in the ceiling or wall) and clean or replace the filter. In a Brisbane summer, filters can clog within weeks if you have pets, live near construction, or have not serviced the unit recently.
- •Open the indoor unit panel and remove the filters
- •Wash under running water and let dry completely
- •For ducted systems, check the return air grille filter
- •Replace disposable filters — do not try to wash them
- •Clean filters every 2–4 weeks during heavy use periods
Step 4: Check the Outdoor Unit
The outdoor unit (compressor/condenser) is where the heavy lifting happens. If it is not running, your AC will blow warm air or nothing at all. Check that the outdoor unit is actually running — you should hear the compressor and see the fan spinning. If it is not running but the indoor unit is, the outdoor unit may have overheated, tripped on a safety cutout, or have a refrigerant issue. Make sure the area around the outdoor unit is clear — plants, leaves, and debris can restrict airflow and cause overheating. In Brisbane, outdoor units can also overheat if they are in direct afternoon sun without shade. Hosing down the outdoor unit with water can help cool it down.
- •Check the outdoor unit is running (fan spinning, compressor humming)
- •Clear any leaves, debris, or plant growth from around the unit
- •Ensure at least 30 cm of clearance around the outdoor unit
- •Gently hose down the outdoor unit to cool it if overheated
- •If it is making unusual noises, turn it off and call a technician
Step 5: Staying Cool While You Wait for Repair
If your AC needs professional repair and you are waiting for a technician, there are ways to stay comfortable. Close blinds and curtains, especially on north and west-facing windows, to block heat. Use fans to circulate air — even a basic pedestal fan makes a big difference. If you have a second AC unit (such as a bedroom split system), use it as your cool room. Wet a towel and place it over yourself or hang wet sheets in front of a fan for evaporative cooling. Stay hydrated by drinking cold water regularly. If temperatures exceed 40 degrees Celsius and you have vulnerable household members (elderly, very young, or those with medical conditions), consider going to an air-conditioned public space like a library or shopping centre.
- •Close blinds and curtains, especially on north and west windows
- •Use fans to circulate air throughout the house
- •Retreat to a room with a working AC unit if available
- •Hang a wet towel in front of a fan for evaporative cooling
- •Stay hydrated with cold water
- •Consider an air-conditioned public space if vulnerable people are at risk