DIY Troubleshooting If Your Heating Unit Won’t Turn On – What You Can Check Yourself

Before You Call a Plumber — Check These First

If your gas heater won't turn on, there are a few simple things you can check yourself before calling a plumber. Some of these take less than a minute and could save you a service call. Work through them in order.

1. Check the Thermostat Setting

Make sure the thermostat is set to a temperature above the current room temperature. This sounds obvious, but it's the number one cause of "heater not working" calls. If it's a battery-powered thermostat, replace the batteries — dead or low batteries cause erratic operation and can prevent the heater from firing at all. If it's a smart thermostat, check it hasn't lost its Wi-Fi connection or reset to default settings overnight.

2. Check the Power and Gas Supply

Confirm your heater is plugged in and the power point is switched on. Check your switchboard for any tripped circuit breakers. Then check whether other gas appliances in the home are working — if the stove or hot water also has no gas, the issue may be with your gas supply rather than the heater. Contact your gas supplier if this is the case.

3. Check and Clean the Filter

Most ducted gas heaters have a return air filter — a removable panel, usually near the return air grille or on the unit itself. If this filter is heavily clogged with dust and debris, the heater will overheat and shut itself off as a safety measure. Remove the filter, clean it (tap it out or vacuum it), and try again. Filters should be cleaned every 3–6 months. This is one of the most common causes of heating problems that homeowners can fix themselves.

4. Look for a Fault Code on the Display

Modern gas heaters display a fault code on the controller when they shut down due to an internal fault. Write down the code and check your heater's manual — the manual will describe what each code means and whether it's something you can reset yourself or whether it requires a technician.

5. Try Resetting the Unit

Most heaters have a reset button or a reset procedure — usually holding the power button for 5–10 seconds, or switching the unit off at the power point, waiting 30 seconds, and turning it back on. Check your manual for the specific reset procedure for your model.

When to Call ATC Plumbing

If you've worked through all of the above and the heater still won't run — or if you can smell gas at any point — stop and call a licensed gas fitter. Do not attempt to disassemble or repair gas components yourself. Gas work is licensed work in Victoria for good reason.

ATC Plumbing's licensed gas fitters diagnose and repair all major heater brands across Melbourne's south-east. Same-day service available. Call 1300 282 758.

Related reading: https://www.atcplumbing.com.au/post/gas-heater-not-working-melbourne-troubleshooting-guide (gas heater not working), https://www.atcplumbing.com.au/post/why-does-my-gas-heater-keep-turning-off-melbourne-troubleshooting-guide (heater keeps turning off), https://www.atcplumbing.com.au/post/are-gas-heaters-safe-what-every-melbourne-homeowner-should-know (gas heater safety). Book at https://www.atcplumbing.com.au/services/gas-heater-service.