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Noritz Tankless Error Code Troubleshooting

Note: This post may contain affiliate links. This means that at no cost to you, we may receive a small commission for made purchases.

Some Noritz problems can be fixed by a typical homeowner with a basic set of tools while others will require the services of a licensed professional. If you don’t feel 100% comfortable in attempting to fix the problem yourself, you can simply get a free, no-obligation quote from a local plumber to help you with your decision. Tankless water heater maintenance is different from traditional models so get professional help if you’re not sure.

NOTE: Below are some of the most common Noritz tankless water heater error codes you may see. You particular Noritz model may show codes different from what is below. In that case, please consult your owner's manual.

Have a different tankless water heater brand that needs troubleshooting?


Noritz Tankless Water Heater Error Codes

Error Code 05
What it Means: Service warning.

How to Fix: This is an automatic service reminder letting you know that it's time to call a licensed Noritz technician. Do not reset the error code prior to the service or the water heater may prematurely fail.

Error Code 10
What it Means: The power drops or gas combustion continues even after the unit is turned off.

How to Fix: Look for foreign materials (ie: oil or grease) on the burner which are still burning after gas combustion stops. To reset the code, turn the unit off and then on.

Error Code 11
What it Means: Ignition failure in your tankless water heater.

How to Fix: Check the gas pressure for correct values. Look for any obstructions in the vents as the fresh air supply might be being blocked. Remove any foreign materials from the ignition rod. Confirm there is no loose wiring in the ignition.

Error Code 12
What it Means: The tankless unit has a weak flame and the water is not being properly heated.

How to Fix: Confirm that there is enough airflow for proper gas combustion. Check that the flame rod/sensor is not covered by debris. Clean or replace if necessary.

Error Code 14
What it Means: The thermal fuse has failed.

How to Fix: Replace the thermal fuse. Confirm that the unit has no airflow restrictions and gas has proper combustion. Check water quality as hard water or sediment can cause the heat exchanger to get clogged. Flush the heat exchanger if necessary.

Error Code 16
What it Means: Water temperature is too high.

How to Fix: Since this is most often caused by hard water or scale buildup, a descaling procedure should be performed. To reset the code afterwards, unplug the water heater for 20 seconds and plug it back in.

Error Code 20
What it Means: High limit switch has been activated.

How to Fix: Check high limit switch and replace if necessary. Otherwise, perform the descaling procedure.

Error Code 29
What it Means: Water level in neutralizer is not properly draining making the water level exceed the correct level.

How to Fix: Make sure the condensate drain line is properly routed and unobstructed. Confirm condensate piping is the correct size and properly sloped.

Error Code 31
What it Means: Inlet (cold water) thermistor failure.

How to Fix: Replace inlet thermistor.

Error Code 32
What it Means: Outlet (hot water) thermistor failure.

How to Fix: Replace outlet thermistor.

Error Code 33
What it Means: Heat exchanger thermistor failure.

How to Fix: Replace the heat exchanger thermistor.

Error Code 45
What it Means: Water leak.

How to Fix: Close the water inlet valve and call for service if you notice a leak. If no visible leak, unplug the unit for 30 seconds to reset it and see if the code clears itself.

Error Code 59
What it Means: Low gas BTU input causing combustion problems.

How to Fix: Confirm correct gas pressure set and properly set for elevation where it's installed. Make sure enough airflow is getting to the combustion chamber by removing any noticable blockage of the vents. Clean fan motor and burner chamber.

Error Code 61
What it Means: Fan motor failure.

How to Fix: Check voltage coming to the fan motor. Replace fan motor or circuit board if necessary.

Error Code 65
What it Means: Main flow control valve failure.

How to Fix: Check for blockage and replace main flow control valve if necessary.

Error Code 66
What it Means: Bypass flow control valve failure.

How to Fix: Check for blockage and replace bypass flow control valve if necessary.

Error Code 67
What it Means: AGM (Air Gas Mixer) abnormality.

How to Fix: Turn the unit off then on. If the code reappears, the air gas mixer will likely need to be replaced.

Error Code 70
What it Means: Circuit board failure.

How to Fix: Replace circuit board.

Error Code 71
What it Means: Abnormality in gas valve drive circuit.

How to Fix: Confirm correct voltage. This error code is often seen when unit is connected to a generator or battery backup or if there is another type of voltage fluctuation. Install a power surge protector if necessary.

Error Code 72
What it Means: Flame rod detection abnormality.

How to Fix: Confirm that the water heater is properly grounded. Check for a damaged circuit board, flame detection circuit, or wires, and replace if necessary.

Error Code 73
What it Means: Improper circuit board setting.

How to Fix: Most likely a jumper connection or dip switch was changed on the circuit board while under power or the circuit board was improperly programmed. Unplug the unit for 30 seconds and plug back in. If the error code still shows up, call a licensed service tech.

Error Code 90 and 91
What it Means: Gas combustion abnormality.

How to Fix: Check airflow obstruction and improper gas burning. Confirm correct air/fuel mixture and gas pressure. Once fixed, reset the unit by unplugging for 30 seconds.

Error Code 92 and 93
What it Means: Neutralizer is at the end of its life cycle.

How to Fix: Replace neutralizer and reset burner timer.

Error Code 760
What it Means: Remote controller problem.

How to Fix: Check for loose wires and confirm only one remote is connected the the water heater. Unplug the unit for 30 seconds to reset.

Error Code 903
What it Means: Abnormal combustion.

How to Fix: Confirm nothing is obstructing the intake or exhaust pipe.

Error Code 941 and 942
What it Means: Exhaust temperature is too high.

How to Fix: Check for and clear any air blockages and reset unit. If that doesn't work, call a licensed service tech.

Error Code F76
What it Means: Communication error between two tankless water heaters using Quick Connect cord.

How to Fix: Confirm that only one remote control is hooked up when multiple units are connected together. Unplug the unit for 30 seconds and plug back in to reset it.

author avatar
Anthony Barnes
Anthony Barnes is the founder of Water Heater Hub and a second-generation plumber by profession. Before developing Water Heater Hub, Anthony Barnes was a full-time plumber, and he has undertaken a wide variety of projects over the decades. As a second-generation plumber, it was easy for Anthony to get used to the technicalities of all from a tender age


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