Noritz Error Codes

Your safety is our #1 priority. Contact Happy Plumbing for further troubleshooting. Our technicians can help you diagnose the problem.

Please note: Your water heater model may use different codes or may provide error codes that are not given here. Therefore you’ll want to consult the manual for your specific heater.

Error Code


Noritz Code 05Service Warning (Turns on automatically when service is due)
Call Happy Plumbing service technician for regular service.
Noritz Code 10The problem in gas combustion causes the power level to drop, while the combustion continues even after shutdown.
Check for foreign materials found on the burner which is burning after gas combustion stops. (Clean the burner if dirty)
Check for blocked exhaust flue.
To reset the error code 10, the power must be disconnected
If there is a recirculation loop use an aquastat to keep 10-degree differential.
Turn the unit off, then back on.
Noritz Code 11Ignition Failure.
Check that the gas valve opens.
Press the power button to turn the unit off, open a hot water faucet, and turn the unit back on.
If the error code no longer flashes the problem is solved.
Check for blocked combustion air supply. Check for debris on the gas burner or gas supply orifice.
Check for proper gas type (LP vs Natural gas), pressure, free flow through gas piping and valves, clean flame rod (ignition rod),
assure no blockage in vent or vent connector, and clean ignition plug.
Noritz Code 12Burner flame loss during operation, or Bad flame detection rod.

Weak flame.
Check for proper gas pressure, free flow, and no blockage in the vent.
Check for adequate combustion air.
Clean ignition plug & flame sensor rod.
Also, see Noritz error code 11.
Noritz Code 14Thermal fuse failure.
Replace the thermal fuse.
The thermal fuse is a white cord that wraps around the heat exchanger.
Failure cause: scaled or dirty heat exchanger,
Check for obstructed combustion airflow, and clean proper burner operation.
Check water quality for hardness or sediment that can clog the heat exchanger. Flush scaled heat exchanger. Use a scale remover if needed.
Noritz Code 16Extremely high water temperature.
Watch out: excessive Noritz hot water temperature is a dangerous scalding hazard.
Check for sediment or scale clogging and clean or de-scale the unit using a cleaner such as vinegar or a de-scaler.
Check manifold pressure adjustment.
Noritz Code 20High-limit switch activated.
Check or replace the high-limit switch.
Check for scale and de-scale the heater.
Noritz Code 21Pressure switch abnormality.
Check/replace the pressure switch.
Check fan motor operation.
Check for blocked exhaust flue.
Noritz Code 29High water level in neutralizer; neutralizer clogged. Condensate drainage problem.
Check for clogged condensate drain; check for damp or wet or damaged water level sensor.
Check for frozen neutralizer due to condensate clogging.
Noritz Code 31Inlet thermistor failure.
Replace the inlet thermistor.
Noritz Code 32Outlet thermistor failure.
Replace the outlet thermistor.
Noritz Code 33Heat exchanger thermistor failure.
Replace the heat exchanger thermistor.
Noritz Code 410Multi-system flow imbalance error.
Check the blocked heater flow
Check heater filter
Check the flow sensor for damage or debris
Noritz Code 45Water leak.
Close the water supply valve.
Look for water leaks.
If no leak is seen, unplug the heater for 30 seconds or more, then re-connect.
If the error code clears continue use; else call Happy Plumbing for service.
Noritz Code 51Noritz Code 51: Gas Manifold Solenoid Failure
A reader opined that for some models this code means Noritz manifold replacement is needed.
See Error Code 59 below.
Noritz Code 56CCP Valve abnormality
Check for blocked heater flow/obstructions
Check CCP valve via the system controller & replace uncertain CCP valve
Noritz Code 57Not listed, check that you are reading the code correctly, then contact the company directly.
Noritz Code 59Low input BTU, insufficient gas supply, combustion problems such as obstructed exhaust flow.
Check for blocked exhaust flue.
Check for adequate combustion air; check for blocked exhaust venting; clean fan motor & burner chamber.
Check for a stuck exhaust damper or too-long or too many elbows in exhaust vent.
Check that the heater is properly set for the elevation where installed.
Occurs if natural gas pressure is below 5″ WC or propane below 8″ WC.
Noritz Code 61Fan motor failure.
Check the voltage of the fan motor.
Replace the faulty fan motor or faulty circuit board (that controls the fan).
Noritz Code 63Recirculation Abnormality – Condensing Tankless Gas Water Heater NRCR111DV & NRCR92DV
Check the return line filter.
Check the crossover valveā€™s filter.
Noritz Code 65Main flow control valve abnormality
Check for blockage of the main servo
Check the operation of the main servo
The main servo may need to be replaced
Noritz Code 66Bypass flow control valve failure.
Check for blockage of the bypass servo valve or replace the valve.
Nortiz Code 67AGM (Air-Gas Mixer) abnormality.
Turn power off, wait 30 seconds, turn power on. If code clears, continue use.
If code reappears, replace the AGM
Noritz Code 70Circuit board fault.
Replace the circuit board.
Noritz Code 71Gas valve drive circuit abnormality.
The water heater is connected to battery backup, solar power, or generator, and the voltage supply is not stable.
Check the voltage delivered from the circuit board.
Check the unit’s electrical ground continuity.
In areas of unstable power, install a power surge protector.
Noritz Code 72Flame rod flame detection error: flame detected without proper ignition sequence.
Check for proper electrical ground. Check for the damaged circuit board. Check for damaged flame detection circuit/wires
Noritz Code 73Circuit board setting error.
Reset the unit by disconnecting the power. Review & correct circuit board programming/switches.
Common cause: connection changed with power on.
Check for circuit board damage
If failure persists replace the circuit board.
Noritz Code F76Multi-system communication error. Breakdown in communication between two tankless water heaters using the Quick Connect Cord.
Disconnect the power to reset the unit. Check cord connections.
Make sure that only one remote control is hooked up when two units are connected.
Noritz Code 760Remote controller problem.
Check for loose wire connections.
Reset the unit. Unplug from power, wait 30 seconds, and re-connect.
Check that only 1 remote controller is connected to the heater.
Noritz Code 90 / 99Combustion gas alert.
Check for proper gas flame color (light blue, yellow tips). Check for the blocked flue, and dirt on the gas burner.
Have a professional check the gas supply pressure.
Noritz Code 90Combustion gas problem.
Check for proper combustion air, check flame color – as per code 90/99 above.
To reset the Noritz error code: unplug the unit for 30 seconds, then re-connect.
Noritz Code 92, 93Neutralizer near the end of life
Replace the neutralizer immediately
Noritz Code F90Combustion gas alert. (Improper air-fuel mix)
Check for blocked exhaust flue.
Check for debris in the fan motor.
Have a professional check the gas supply pressure.
Check vent length, bends, elbows, draft, dip switches.
Noritz Code 903Combustion abnormality
Check combustion airflowCheck combustion flame, gas supply
Check the exhaust vent for blockage
Noritz Code 941, 942Excessive exhaust temperature
Check combustion air supply for blockage
Check the exhaust vent for blockage
Call for service/repair.
Noritz Code F99Check for blocked exhaust flue.
Noritz Code 92 / 93
Noritz Code F92
Noritz Code F93
Neutralizer life cycle alert.
Replace the neutralizer & reset the burner timer.
Noritz Error Code C or CF
Noritz Code CF1 CF2 CF3 or CF4
Noritz Code CFH
Scale blockage of the heat exchanger.
The heater will be locked off.
Flush & clean the heat exchanger.
You may need to hire a trained service technician to use a scale-removing cleaner or chemical.
Heat exchanger replacement is needed in severe cases.
Noritz Code H nn
H followed by 2 numeric digits
Scale blocked heat exchanger, detected after re-connecting electrical power