Rinnai is Australia's most popular gas heater brand and one of the most commonly serviced brands in Melbourne homes. When a Rinnai heater develops a fault, it tells you about it through a system of error codes, displayed as a numbered code on digital display models or as a sequence of flashing lights on older models.
This guide covers every major Rinnai error code, explains what is causing it and tells you exactly what to do. It applies to Rinnai wall furnaces, space heaters and continuous flow hot water units.
What it means: The Rinnai heater has attempted to ignite and establish a burner flame, but the flame has failed to establish or has gone out during operation.
Common causes
- Dirty or partially blocked burner jets restricting gas flow to the flame
- Faulty flame sensor (thermocouple or thermopile) not detecting the flame correctly
- Gas supply issue check other gas appliances are working
- Faulty gas valve not allowing sufficient gas flow
- Draught or air movement extinguishing the flame (unflued models)
What to do: Check gas supply first by testing another gas appliance. Try one reset. If code 03 returns, call us for a same-day diagnosis. Repeated flame failure without intervention indicates an underlying fault that requires professional repair.
Important note on code 03: Do not continue resetting a heater showing code 03. If the gas valve is allowing gas flow during a failed ignition attempt and the system is resetting before the gas disperses, this can create a gas accumulation risk.
What it means: The heater has attempted to ignite multiple times but has failed to establish any flame at all. This is different from code 03: code 03 means the flame went out after establishing, code 11 means no flame was established at all.
Common causes
- Gas supply issue the most important first check
- Faulty ignition module or spark igniter not producing a spark
- Dirty or corroded pilot assembly preventing gas from reaching the igniter
- Faulty gas valve not opening
- PCB (printed circuit board) fault
- Extremely low gas pressure
What to do: Check that other gas appliances in the home are working. If gas supply is confirmed, try one reset. If code 11 returns, call us. Ignition failure that persists after one reset requires professional diagnosis, it is not something to keep resetting through.
What it means: The heater ignited briefly, the flame was established, but then went out within seconds of startup, before stable operation was achieved.
Common causes
- Dirty or contaminated flame sensor not detecting the startup flame reliably
- Faulty thermocouple or thermopile (on models with a standing pilot)
- Weak or unstable flame caused by a partially dirty burner
- Intermittent ignition issue
What to do: Try one reset. If code 12 returns, call us for a flame sensor diagnosis. This code is more commonly resolved than code 11 as it typically indicates a sensor or clean issue rather than a complete ignition failure.
What it means: The heater has entered safety lockout after multiple failed ignition attempts. This is a cascading fault: code 14 typically follows repeated code 11 incidents that have not been resolved.
Common causes
- The same root causes as code 11 but now the heater has locked out as a safety measure after repeated failures
- The heater has been reset multiple times without resolving the underlying fault
What to do: Do not continue resetting a heater in lockout. The lockout is a safety feature. Call us to diagnose and resolve the underlying ignition fault before clearing the lockout. Clearing a lockout without fixing the root cause simply results in the same fault cycle repeating.
What it means: The temperature sensor (thermistor) in the heater is reading an incorrect temperature or has failed. The heater cannot reliably determine its operating temperature.
Common causes
- Faulty thermistor component the sensor itself has failed
- Wiring fault between the thermistor and the PCB
- PCB fault affecting the thermistor circuit
What to do: This is an electronic fault requiring professional diagnosis. Call us. A thermistor replacement or PCB repair is typically required.
What it means: The heater has detected an overtemperature condition at the burner or heat exchanger and has shut down to prevent damage or a safety hazard.
Common causes
- Blocked return air filter (ducted systems) the most common cause by far
- Blocked or restricted duct work or vents
- Insufficient ventilation around the unit
- Fan motor fault reducing airflow
- Faulty overheat thermostat
What to do: Check and clean the return air filter immediately on ducted systems. Ensure all room vents are open and unobstructed. If the code clears after cleaning the filter, monitor the system. If code 31 returns after cleaning, call us: there may be a fan motor issue or a more serious airflow problem.
What it means: The flue or combustion gases are reaching an unsafe temperature. This indicates a flue system issue: either the flue is partially blocked or the combustion gases are not venting correctly.
Common causes
- Blocked or partially blocked external flue terminal (bird nesting, debris, spider webs)
- Damaged flue pipe with a partial collapse or blockage internally
- Faulty flue overheat thermostat
- Incorrect flue installation or damaged flue components
What to do: This is a safety issue. Do not continue using the heater. Check the external flue terminal for visible blockage. Call us for a flue inspection and repair. A flue overtemperature condition means combustion gases are not being safely vented, this carries a CO risk.
What it means: The heater's fan motor is not operating correctly, either not running, running too slowly or not reaching the required speed during the startup sequence.
Common causes
- Faulty fan motor
- Worn or failed fan motor bearings
- Fan motor capacitor failure
- Wiring fault to the fan motor
- Fan obstruction (debris inside the unit)
What to do: A fan fault requires professional repair. Do not continue operating a heater with a confirmed fan fault, without correct airflow, the heat exchanger overheats. Call us for a same-day fan motor diagnosis and repair.
What it means: The gas valve is not operating correctly, either failing to open to allow gas flow or failing to close correctly.
Common causes
- Faulty gas valve component
- Wiring fault to the gas valve
- Low gas pressure preventing the valve from operating correctly
- PCB fault affecting gas valve control
What to do: Do not continue resetting a heater showing a gas valve fault. Call us. A gas valve fault means either the heater is not receiving gas (ignition failure) or, in rare cases, the valve may not be closing fully (potential gas accumulation risk). Professional diagnosis is required.
What it means: The heater's main printed circuit board has detected an internal fault. The PCB controls all electronic functions of the heater.
Common causes
- PCB component failure due to age or power surge
- Wiring fault causing an incorrect signal to the PCB
- Manufacturing defect (rare on newer units)
What to do: PCB faults require professional diagnosis. In some cases the PCB can be repaired by replacing a specific component. In others, full PCB replacement is required. Call us for a diagnosis and quote.
Rinnai Infinity continuous flow hot water units have their own error code system. The most common codes are:
Error Code 11 (Infinity): Ignition failure on the hot water unit. Check gas supply. Try one reset. If it returns, call us.
Error Code 12 (Infinity): Flame failure during operation. Try one reset. If it returns, call us for a flame sensor diagnosis.
Error Code 76: Temperature sensor fault on the heat exchanger or outlet. Requires professional diagnosis. Call us.
