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There is never a good time for your gas heater to stop working, but it almost always seems to happen on the coldest night of the year. As a trusted plumber Sydney households call when their heating fails, Hero Plumbing has diagnosed and fixed thousands of gas heater faults. This guide walks through the most common reasons a gas heater won’t turn on, what you can safely check yourself, and when you need to call a professional for gas heater repairs in Sydney.
Why won’t my gas heater turn on?
Before calling a technician, it is worth running through the basics. Common first checks include whether the heater is switched on at the wall, whether the thermostat is set above the current room temperature, and whether the gas supply to the property is active. If your stove or other gas appliances are also not working, you likely have a supply issue rather than a heater fault.
Faulty thermocouple
The thermocouple is a safety device that detects whether the pilot light is lit. When working correctly, it generates a small electrical signal that keeps the gas valve open. When the thermocouple fails, it incorrectly signals that the pilot is out and shuts off the gas supply, even if the pilot is lit.
Signs of a faulty thermocouple include the pilot light staying lit briefly then going out, the heater failing to stay on after ignition, and error codes on digital models. Thermocouple replacement is a relatively straightforward repair for a licensed technician and is one of the most common gas heater fixes.
Pilot light problems
On older gas heaters with a standing pilot system, a pilot light that keeps going out is one of the most common faults. Possible causes include:
- A dirty or blocked pilot orifice restricting gas flow
- A draught blowing out the flame
- Low gas pressure
- A worn thermocouple (see above)
Relighting a pilot light is typically something a homeowner can do safely by following the manufacturer’s instructions. However, if the pilot repeatedly goes out after relighting, the underlying cause needs professional diagnosis.
Ignition failure
Modern gas heaters use an electronic ignition system instead of a standing pilot. These systems generate a spark to light the burner on demand. Ignition failures can be caused by:
- A worn or dirty igniter electrode
- A faulty ignition control board
- Moisture or corrosion on the ignition components
- A broken ignition wire
Ignition system repairs require access to internal components and should be carried out by a licensed gas fitter. Learn more about how gas heaters work to understand the ignition process.
Gas supply issues
If the heater appears to attempt ignition but the burner does not light, or the flame is very weak, the issue may be with the gas supply itself. Possible causes include:
- The gas meter isolation valve being partially or fully closed
- Low gas pressure from the distribution network (contact your gas supplier)
- A kinked, blocked, or damaged flexible gas connector behind the heater
- A faulty gas pressure regulator
Blocked or dirty burner
Over time, dust, debris, and combustion by-products can accumulate on the burner assembly. A dirty burner can prevent clean ignition, produce a weak or uneven flame, or cause the heater to shut down on its safety limit switch. Annual servicing from Hero Plumbing’s gas heater service team includes a full burner clean and inspection.
Safety limit switch tripping
Gas heaters have high-temperature limit switches that shut the unit down if it overheats. An overheating heater can be caused by blocked air vents, a dirty filter, or a failing heat exchanger. If the heater shuts down shortly after starting and feels very hot to the touch, check that vents and air intakes are not blocked.
When to call a licensed gas fitter
You should call a licensed gas fitter if the pilot light or ignition system has been checked and the problem persists, there is any smell of gas, the heater is making unusual noises, the heater is repeatedly shutting itself down, or the unit is more than 10 years old and has never been serviced.
Hero Plumbing provides gas heater repairs in Sydney for all major brands including Rinnai, Rheem, Everdure, Paloma, and Omega Altise. We also recommend reading our guide on servicing a gas heater to understand what a full service involves.
Book a gas heater repair in Sydney
If your gas heater stopped working and the basic checks have not resolved the problem, call Hero Plumbing. We carry out same-day and next-day gas heater repairs across Sydney, diagnosing faults accurately and getting your heating back on as quickly as possible.
Frequently Asked Questions
Why won’t my gas heater turn on?
The most common causes are a faulty thermocouple, pilot light that has gone out, ignition failure, or a gas supply interruption. Check that the gas supply is on and the thermostat is set correctly before calling a technician.
Why does my gas heater keep going out?
A heater that keeps switching off is usually caused by a faulty thermocouple, a dirty pilot orifice, a tripping safety limit switch, or a gas pressure problem. A licensed gas fitter can diagnose and fix the underlying cause.
Can I relight the pilot light myself?
Yes, in most cases. Follow the manufacturer’s instructions on the heater label. However, if the pilot repeatedly goes out after relighting, there is an underlying fault that needs professional diagnosis.
How much does it cost to repair a gas heater in Sydney?
Costs vary depending on the fault. Simple repairs such as thermocouple replacement are relatively affordable, while ignition board replacement or heat exchanger repairs cost more. Hero Plumbing provides upfront pricing before any work begins.
Is it worth repairing an old gas heater?
It depends on the age and condition of the unit. If a heater is more than 12 to 15 years old and requires significant repairs, replacement is often more cost-effective. Our technicians will give you an honest assessment.
