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Noritz Tankless Error Code Troubleshooting

Is your Noritz water heater flashing an error code at you? Here’s how to troubleshoot it.

Tankless water heaters have transformed the way we live, providing a steady stream of hot water whenever we need it. They mean we no longer have to maintain an entire tank of water that is always hot but won’t all be used.

However, they aren’t flawless and they can sometimes encounter problems. Noritz has addressed this by making its tankless heaters provide error codes, but these aren’t much use if you don’t know what they mean.

Learning how to decipher Noritz error codes might mean you can fix the problem yourself, without needing an expensive service call out. In this article, we have listed the error codes, what they mean, and their recommended solutions.

Key Takeaways

  • Locate error codes on the remote control display.
  • Turn off power and gas before troubleshooting for safety.
  • Common error codes include ignition failure, weak flame, and temperature spike.
  • Consult the owner’s manual for specific solutions to each error code.

Where Do I Find the Error Code?

Noritz tankless water heaters include a remote control for convenient, user-friendly operation. You can use this controller to set your ideal water temperature, turn your water heater on or off, and set the flow meter alarm.

The display on the remote control is where an error code will be shown when something is wrong with your heater. The number will appear where you would normally see the water temperature. If you have no display or it isn’t working, you should check the power supply or call a professional.

Noritz Tankless Error Code Troubleshooting


Troubleshooting error codes on a tankless water heater involves working around electricity and gas. For safety reasons, make sure you turn off the power and gas before carrying out any maintenance. If you have any uncertainty about what you are doing, call a professional technician instead.

Error Code 05

What It’s Telling You

  • This is a service warning.

The Solution

  1. This automatic reminder states that it is time for your water heater to be serviced by a qualified Noritz technician. Do not attempt to reset this error code before the service is carried out. Doing so could lead to your water heater failing.

Error Code 10

What It’s Telling You

  • The power has dropped, or gas combustion is still occurring after the unit has been turned off.

The Solution

  1. Check the burner for debris: Materials such as oil or grease might continue burning after the gas combustion has stopped.
  2. Clean the burners: Wipe away any debris.
  3. Reset the water heater: Turn the unit off, wait 30 seconds, and then turn it back on. If you’re unsure how to reset your Noritz tankless water heater, consult the owner’s manual.

Error Code 11

What It’s Telling You

  • There is an ignition failure.

The Solution

  1. Gas pressure: Make sure the gas pressure matches that in your owner’s manual and that the supply is open.
  2. Inspect for blockages: Check the vents to see if anything is preventing proper airflow.
  3. Ignition rod: Make sure the ignition rod is free from debris and foreign materials.
  4. Wiring to the ignition: Ensure the wiring to the ignition is not loose or damaged.

Error Code 12

What It’s Telling You

  • The flame is too weak and not sufficient to heat the water.

The Solution

  1. Airflow: Ensure there are no blockages preventing proper combustion.
  2. Flame rod/sensor: Remove any debris.
  3. Replace the flame rod: If it can’t be cleaned or is faulty.
  4. Adjust the airflow or gas valve: This will help create a strong enough flame.

Error Code 14

What It’s Telling You

  • Failure of the thermal fuse.

The Solution

  1. Thermal fuse: The thermal fuse might have burnt out. Replace it with a new one.
  2. Blockages in the airflow: Make sure there are no obstructions in the airflow, and that the gas is combusting properly.
  3. Heat exchanger: Inspect the heat exchanger to make sure it hasn’t become clogged by sediment.
  4. Flush: Follow the manufacturer’s instructions to flush the heat exchanger.

Error Code 16

What It’s Telling You

  • The water temperature has suddenly spiked and is too high.

The Solution

This is most commonly caused by a build-up of scale in the system, often the result of hard water (1).

  1. Descale the unit: Do this using white vinegar, according to the boiler manufacturer’s instructions.
  2. Reset the code: Once descaled, disconnect the unit’s power supply. Wait 20 seconds and reconnect it.

Error Code 20

What It’s Telling You

  • The high limit switch that initiates the thermostat cut-off has been activated.

The Solution

  1. Replace the high limit switch: Check for damage to the switch and replace it if necessary.
  2. Descale the unit: Follow your user manual to descale your unit.

Error Code 29

What It’s Telling You

  • The water level has exceeded its usual limit because the water level neutralizer is not draining correctly.

The Solution

  1. Examine the drain line: Make sure there is no condensate or other obstructions and that it is properly routed.
  2. Check the condensate piping: Verify that the piping is the right size and is sloped correctly.

Error Code 31

What It’s Telling You

  • The cold water thermistor on the inlet pipe has failed.

The Solution

  1. The sensors in the thermistor have failed. Replace it.

Error Code 32

What It’s Telling You

  • The hot water thermistor on the outlet pipe has failed.

The Solution

  1. The sensors have failed. Put a new thermistor in.

Error Code 33

What It’s Telling You

  • The thermistor on the heat exchanger has failed.

The Solution

  1. The sensors have failed. Replace this component.

Error Code 59

What It’s Telling You

  • The BTU (British thermal unit) input from the gas is too low, causing combustion issues.

The Solution

  1. Check the gas pressure: Make sure the gas pressure is correct and appropriately set for the water heater and its location. Your owner’s manual will tell you the correct settings.
  2. Check the vents: Inspect the combustion chamber vents for blockages and airflow issues.
  3. Clean the burner chamber and the fan motor: Ensure there is no debris on these components and clean them if necessary.

Error Code 61

What It’s Telling You

  • The fan motor has failed.

The Solution

  1. Is the voltage correct? Check the voltage supplying the fan motor.
  2. Replace the circuit board: If the voltage is insufficient, replace the circuit board.
  3. Replace the fan motor: If the voltage is sufficient, replace the fan motor.

Error Code 65

What It’s Telling You

  • The main flow control valve has failed.

The Solution

  1. Obstructions: Check for any blockages in the vents and remove them.
  2. Main control valve: Replace the control valve.

Error Code 66

What It’s Telling You

  • There has been a failure of the bypass control valve.

The Solution

  1. Obstructions: Check for any blockages in the valve.
  2. Renew: Replace the bypass control valve if needed.

Error Code 67

What It’s Telling You

  • Abnormality in the air-gas mixer (AGM).

The Solution

  1. Cut the power: Turn the water heater off and back on.
  2. Error code reappearance: If the error code still appears, replace the air-gas mixer.

Error Code 70

What It’s Telling You

  • The circuit board has failed.

The Solution

  1. Replace the circuit board with a new one.

Error Code 71

What It’s Telling You

  • There is something wrong with the gas valve drive circuit.

The Solution

  1. Check that the voltage is correct for the unit. This error often occurs if the heater is powered by a generator or battery backup, or if there has been a power surge or voltage change. Installing a power surge protector can prevent this.

Error Code 72

What It’s Telling You

  • There is something wrong with the flame rod detection.

The Solution

  1. Proper grounding: Check that the heater is properly grounded.
  2. Damage: Ensure that the flame detection circuit, circuit board, and wires are not damaged.
  3. Renew: Replace any damaged parts.

Error Code 73

What It’s Telling You

  • The circuit board is not set correctly.

The Solution

This could be caused by improper programming or replacing a dip switch or jumper connection with the power on.

  1. Cut the power: Unplug the heater for 30 seconds.
  2. Return the power: Plug it back in and turn it on.
  3. Error code still shows: If the error code persists, call out a qualified technician.

Error Code F76

What It’s Telling You

  • This is an error in communication between multiple heaters when they are connected by a quick connect cord. More than one remote control connected to the units can cause a malfunction.

The Solution

  1. Check the remote controls: Ensure only one remote control is operating the multiple heaters.
  2. To reset the code: Unplug the units for 30 seconds and then power them back on.

Error Code 760

What It’s Telling You

  • There is a problem with the remote control.

The Solution

  1. Is the wiring good? Check the unit for loose wires.
  2. Check the remote controls: Make sure only one remote is connected to multiple heaters.
  3. Reset the code: Unplug the heater for 30 seconds, and then plug it in again.

Error Codes 90 and 91

What They’re Telling You

  • Abnormality in the gas combustion.

The Solution

  1. Blockages: Check for any obstruction in the air flow or gas flow.
  2. Correct air/gas mix: Make sure the combination of the gas/air mix is in line with your owner’s manual.
  3. Check for debris: Ensure there is no dirt in the fan motor or fuel vents.

Error Codes 92 and 93

What They Are Telling You

  • The neutralizer has reached the end of its lifespan.

The Solution

  1. Replace the neutralizer: Install a new neutralizer according to your owner’s manual.
  2. Reset the burner timer: Follow the instructions in your owner’s manual.


How Do You Troubleshoot a Noritz Water Heater?

The Noritz digital remote control largely eliminates the guesswork from troubleshooting their water heaters. When something goes wrong, the remote will display an error code in the space where you can usually see the current water temperature. This corresponds to a particular problem and should tell you the exact issue, or at least narrow it down significantly.

How Long Does a Noritz Tankless Water Heater Last?

Noritz tankless water heaters are renowned for their reliably long lifespans. This is even in comparison to other tankless water heaters, which are known to last significantly longer than tank-type heaters. A Noritz tankless water heater should last you as long as 20 years and could continue working beyond this with proper maintenance and a soft water supply.

Who Makes Noritz Water Heaters?

In the United States, Noritz water heaters are produced by Noritz America, which is the US subsidiary of Noritz Japan. Noritz was originally founded in Japan in 1951, with an emphasis on using cutting-edge technology to heat people’s water when bathing. Today, the company focuses on tankless water heaters and is one of the largest tankless heater brands in the world.

What Is the Most Common Problem With Noritz Tankless Water Heaters?

There are 5 common problems with Noritz tankless water heaters. Error code 11 indicates your tankless water heater has experienced an ignition failure.

It indicates that your device is not lighting up to heat the water, which is a problem that might be caused by an inadequate supply of gas, an inadequate movement of air, or debris on the ignition plug.

When you get the error code 12, it indicates that your appliance has a weak flame and that prevents proper water heating. This issue, like code 11, is brought on by inadequate gas or airflow in the system.

Code 16 will be generated if there is a sudden jump in the outlet water temperature. This is typically the consequence of scale buildup, which hinders the efficiency of heat transfer and makes your water heater work extra to compensate.

An error code 73 will be generated if the settings on the circuit board are incorrect. An improper combustion process that is brought on by an inadequate proportion of air to fuel will result in code 90.

There may not be enough gas, there may be an obstruction in the fuel vent, or there may be debris in the fan motor. These are all potential causes.

Why Does My Noritz Tankless Water Heater Keep Shutting Off?

The majority of the time, a Noritz tankless water heater keeps shutting off due to insufficient water flow. The tankless water heaters manufactured by Noritz are subject to a minimum flow of 0.5 gpm for most of their models.

Check that the heater is receiving all of its necessary supplies, including electricity, water, and gas. Try bringing the water temperature down to 120 degrees Fahrenheit.

How Do I Reset a Noritz Error Code?

To reset a Noritz error code, you need to know what code you’re dealing with first. For example, if you’re experiencing a code 10, then you have to disconnect the power.

If you’re dealing with an error code 90, you should unplug the unit for half a minute and then reconnect the power supply.

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About the Author

Peter Gray

Peter has been a homeowner for 35+ years and has always done his own repair and improvement tasks. As a retired plumber, Peter now spends his time teaching others how they can fix leaks, replace faucets, and make home improvements on a budget.