Ducted heater not firing: what to check before you call
The five things to check when a gas ducted heater will not start, which ones you can fix yourself, and when to call for a same-day repair.
Heat Cool Today. Updated 20 October 2026.
Check the controller first
Make sure the controller is set to heat, the temperature is set above the room temperature, and the timer has not switched it off. On a cold morning the set temperature is often lower than the room because someone turned it down the night before. Set it five degrees above the room and wait two minutes.
Check the power and the gas
A ducted heater needs both. Check the switch at the unit or the switchboard has not tripped, and that the gas is on at the meter. If other gas appliances in the house are also out, the problem is the supply, not the heater.
Listen to what it does
If the fan starts but no heat comes, the burner is not lighting. That points to the igniter, flame sensor or gas valve, which are a repair. If nothing happens at all, it is usually power, a fuse, or the control board. If it fires, runs briefly and cuts out, the flame sensor is dirty or the heater is overheating because the filter is blocked.
Check the filter
A blocked return air filter is the most common cause of a heater that runs then cuts out. Pull it out, and if you cannot see light through it, clean or replace it. Then try again.
When to call
If the controller, power, gas and filter are all fine and the heater still will not fire, it needs a technician. Call 0421 830 037. We carry igniters, flame sensors and thermostats, and most of these are fixed on the first visit. If you smell gas at any point, turn the heater off, open the windows and call straight away.