Noritz Error Codes and Troubleshooting guide

Noritz tankless water heaters are efficient and reliable systems that can provide a constant supply of hot water.

However, like any other appliance, they can experience problems and issues that require troubleshooting and repair.

Understanding Noritz error codes is essential to diagnosing the problems that may arise with these units.

In this article, we’ll explore the most common problems with Noritz water heaters, their symptoms, and offer tips for troubleshooting and repairing them.

Noritz tankless water heater

Noritz error codes are represented by two-digit numbers, ranging from 10 to 99. When a failure occurs, the display and operation light will flash together, indicating the error code. In the following text, we will provide information on the most common problems and the corresponding error codes displayed on the remote controller.

Assuming that the water heater is installed correctly, with the appropriate gas type and according to codes, the tools needed to resolve the issues below are mainly a screwdriver, manometer, and voltmeter.

Noritz tankless water heaters come equipped with advanced features and elements that are controlled by an electronic board. Therefore, successful repairs require knowledge and skills.

Noritz Error Codes List: Problems and Repair Tips

Error Code 05

Problem: Service warning.

Solution: Error Code 05 indicates a service warning rather than an error code. This message serves as an automatic reminder that it’s time to call a licensed Noritz technician to perform regular maintenance on your unit. It’s essential not to reset the error code before the service as it may lead to premature failure of the water heater. Therefore, make sure to schedule a service call as soon as possible to ensure your unit continues to operate efficiently.

Error Code 10

Problem: Error Code 10 indicates a problem in gas combustion that causes the power level to drop, even after the shutdown of the unit.

Solution: This issue may arise due to foreign materials found on the burner that continue to burn after gas combustion stops.

To resolve this issue, check the burner for any foreign materials and clean it thoroughly. To reset Error Code 10, disconnect the power source to the water heater. If there is a recirculation loop, use an aquastat to maintain a 10-degree differential between the supply and return water temperature.

Did you know that even one mistake during installation can cause a serious fire or even an explosion!

Error Code 11

Problem: Ignition fails.

Solution: Error Code 11 indicates an ignition failure, which could be caused by a variety of factors. To resolve this issue, start by checking the gas pressure to ensure it meets the manufacturer’s specifications. Additionally, check for any obstructions in the venting system that could be restricting airflow. It’s also essential to ensure that both the flame rod and ignition plug are clean and free of any buildup that could be interfering with the ignition process.

Error Code 12

Problem: Error Code 12 indicates a burner flame loss during operation, where the flame rod fails to detect a flame.

Solution: To address this issue, first, check the incoming gas pressure to ensure it’s at the correct level. Next, check the venting system for any obstructions that may be impeding proper airflow. Lastly, clean the ignition plug and flame rod to remove any buildup that could be interfering with the sensor’s ability to detect the flame.

Error Code 14

Problem: Thermal fuse failure.

Solution: Error Code 14 indicates a thermal fuse failure in the Noritz water heater. To resolve this issue, the thermal fuse must be replaced. It’s also essential to check for any restrictions in air flow and ensure that the gas burns correctly. Poor water quality can also affect the heat exchanger’s function, leading to element replacement, so it’s crucial to flush the system regularly to prevent buildup and maintain optimal performance.

Error Code 16

Problem: Extremely high water temperature.

Solution: Error Code 16 indicates an extremely high water temperature in the Noritz water heater, which could be caused by sediment and limescale buildup. To address this issue, the water heater may need descaling to remove any buildup that could be causing the temperature to rise. Additionally, it may be necessary to adjust the manifold pressure to ensure the system is operating correctly and efficiently.

Error Code 20

Problem: Activation of the high limit switch.

Solution: Error Code 20 indicates that the high limit switch has been activated, which could be due to several reasons. Firstly, check if the high limit switch is working correctly. Secondly, remove any limescale buildup that could be causing the water temperature to rise too high.

Error Code 29

Problem: High water level in the neutralizer and clogging.

Solution: To solve this issue, check that the condensate drain pipe is draining correctly to prevent any blockages. It is also important to ensure that the water level sensor on the neutralizer is free of moisture to prevent freezing of the pipe.

Error Code 31

Problem: Problem with the inlet thermistor.

Solution: Error Code 31 indicates a problem with the inlet thermistor, which measures the temperature of the incoming water. This error can occur when the thermistor is damaged or faulty. To resolve this issue, the thermistor will need to be replaced by a Noritz licensed technician.

Error Code 32

Problem: Problem with the outlet thermistor.

Solution: If your Noritz water heater displays Error Code 32, it means there’s an issue with the outlet thermistor, which is responsible for measuring the temperature of the outgoing water. Typically, this error occurs when the thermistor is damaged or defective. To fix the problem, it’s necessary to replace the thermistor, and we recommend contacting a Noritz licensed technician for assistance.

Error Code 33

Problem: Heat exchanger thermistor malfunction.

Solution: Replace the thermistor.

Error Code 59

Problem: Low input BTU, problems with the combustion.

Solution: This can be caused by inadequate fresh air in the gas combustion chamber or incomplete venting due to blockages in the vents. To resolve this issue, it is necessary to remove any blockages in the venting and clean the fan motor and burner chamber. Additionally, the water heater should be adjusted to the correct height elevation.

Error Code 61

Problem: Faulty fan motor.

Solution: Measure the incoming voltage. Check and replace if needed the fan motor or circuit board.

Error Code 66

Problem: Problem with the bypass flow control valve.

Solution: If there is a blockage of bypass servo, correct it. If the element is not operating correctly, replace it.


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Error Code 70

Problem: Faulty circuit board.

Solution: Replace the circuit board.

Error Code 71

Problem: Gas valve drive circuit abnormality.

Solution: The error code 71 can occur if the water heater is connected to a battery backup, solar power, or generator, and if there is a fluctuation in the voltage supply. Check the voltage output from the circuit board to determine if it has been damaged.

Error Code 72

Problem: The flame rod detects the flame without the ignition sequence.

Solution: The unit must have proper grounding. Check if there is damage to the circuit board and flame detection circuit.

Error Code 73

Problem: The problem with the circuit board setting.

Solution: Reset the heater by disconnecting the power and check the circuit board programming.

Error Code F76

Problem: The communication error for the multi-system.

Solution: Disconnect the power to reset the unit and make sure that the connecting cord is not damaged.

Error Code 760

Problem: Problems with the remote controller.

Solution: Reset the unit, check the wire connections and make sure that only one controller is connected.

Error Codes 90 and 99

Problem: Gas combustion problem.

Solution: To resolve the issue, check if the flame color is light blue. Yellow tips on the flame are allowed, but if the flame is predominantly yellow, it indicates an issue with gas combustion. Additionally, inspect and remove any blockages in the flue vent to ensure proper ventilation.

Did you know that ventilation is vital for gas water heaters – for airflow and to eliminate the risk of carbon monoxide poisoning?

Error Codes 92 and 93

Problem: Neutralizer life cycle alert.

Solution: A neutralizer must be replaced if its lifecycle is about to end; also, you must reset the burner timer.


Being aware of the Noritz error codes that can occur in your tankless water heater can help you quickly diagnose and resolve any issues that may arise.

By following the solutions provided for each error code, you can ensure that your water heater is functioning properly and efficiently.

Additionally, regular maintenance and inspection can prevent many common problems and prolong the life of your water heater. If you encounter any difficulties that you are unable to resolve, it is always recommended to seek the assistance of a licensed professional to avoid any potential safety hazards.


Can I Fix a Noritz Water Heater Error Code Myself?

It depends on the severity of the issue. Some Noritz error codes, such as cleaning the flame rod or resetting the unit, can be done by the homeowner. However, if the error code requires replacing parts or involves electrical or gas connections, it’s best to call a licensed technician.

What Are the Common Problems With Tankless Water Heaters?

Tankless water heaters commonly experience problems such as scale buildup, flow rate issues, ignition failure, overheating, and venting problems. Scale buildup can lead to decreased efficiency and system failure, flow rate issues can result in lukewarm water, and ignition failure can prevent hot water production. Overheating can occur due to thermostat malfunctions or system clogs, while venting problems can create safety hazards like carbon monoxide buildup.

How Often Should I Flush My Tankless Water Heater?

It is recommended to flush your tankless water heater once a year to remove any sediment buildup and maintain optimal performance. However, in areas with hard water, more frequent flushing may be necessary.

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