Navien Tankless Water Heater Error Codes (Troubleshooting Guide)

I have often wondered what exactly the error codes I sometimes get on my Navien tankless water heater mean. Out of curiosity, I began to investigate the different meanings behind the error codes and how they could be resolved.

Navien error codes are meant to indicate the cause of issues with your water heater. These error codes are triggered by certain malfunctions that produce unique error codes. Navien error codes make it easy to identify and resolve issues with your water heater system.

This guide has compiled all of the common Navien error codes in one place so that you can identify your error code quickly and resolve any issues that they entail.

Error codes are built-in descriptions triggered by certain errors experienced by your Navien water heater. These codes each have their unique triggers and descriptions. Using the error code, you will have more insight into the cause of your issue and how to resolve it.

You may be wondering how error codes affect your water heater. This will be covered in the next section.

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How Do Error Codes Affect My Water Heater?

How the error codes affect your water heater will depend on the cause of the code and the issue that it is causing. For example, some error codes could cause your water heater to no longer work properly, while others will allow it to run like normal.

You will need to use this guide to identify your error code before you will know exactly how it will affect your water heater. If your Navien water heater is not working properly, it could be due to several different issues.

Why Is My Navien Water Heater Not Working?

There are many common issues that Navien water heaters might encounter that could make them stop working. These issues include power issues, clogged air vents, damaged gas valves, and other internal component issues.

The error codes provided by your Navien water heater will help you narrow down the cause of your issue and offer you ways to resolve it. These error codes will be detailed in the section below.

Common Error Codes For Navien Tankless Water Heaters

Listed below are some of the most common Navien tankless water heater error codes and some methods to resolve them.  

Error Code E001 – Boiling Water In Heat Exchanger

Error code E001 indicates that there is a significant amount of water inside the heat exchanger and that it is boiling. To resolve this, you should clean the water inlet filter and check the water adjustment valve. If that doesn’t work, consider inspecting and flushing the entire heat exchanger. Finally, check the PCB board and replace it if it is faulty.

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Error Code E002 – Low Water Pressure

Error code E002 indicates low water pressure in the system. This error code will generally resolve itself with no action needed from the user. Once the water pressure returns to normal, the unit will automatically reset itself and clear the error code.

Error Code E003 – Ignition Failure

Error code E003 indicates an ignition failure in the system. To resolve this, check the main gas supply and ensure that it is open. Since gas is involved, it is highly recommended you consult a professional before doing this.

You should also ensure that the power is on and your water heater is plugged in properly. Finally, make sure that the igniter sparks and replace the flame rod if it doesn’t.

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Error Code 004 – False Flame Detection

Error code 004 indicates a false flame detection. To resolve this error code, check to ensure that the power cord is grounded properly and that the ground wire is connected. You should also check to make sure the igniter delivers a spark and replace the flame rod assembly if necessary.

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Error Code E007 & E008 – Faulty Thermistor

Both error codes E007 and E008 indicate a faulty thermistor. To resolve this error, remove the connector from the PCB and measure the resistance of the thermistor. If the resistance between the two red wires of CN13 is from 0.8 to 20k ohm, your thermistor is not the issue, and you should check the connector.

If the thermistor does not fall within this acceptable range, then you will need to replace it with a new one to resolve the error code.

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Error Code E009 – Abnormal Fan Motor Activity

Error code E009 indicates abnormal fan motor activity. To resolve this, check and clean the air filters and fan motor of your water heater. If your fan is pulsing, you may need to replace the fan entirely with a new one.

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Error Code E010 – Abnormal Air Pressure

Error code E010 indicates a venting issue. To address this, simply check the vent pipe and remove any obstructions. You should also clean the air filter and check the air pressure flow sensor for any issues. Finally, if you are unable to locate the problem yourself, consult a professional for more information.

Error Code E011 – High Water Pressure

Error code E011 indicates high water pressure. To resolve this, check the water pressure sensor and replace it if the system doesn’t automatically reset once the pressure is down.

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Error Code E012 – Flame Loss

Error Code E012 indicates a flame loss. To resolve this, check that the main gas line valves are completely open. Also, make sure no obstructions are present in the intake air pipe. You should also check that the unit is properly connected to the power supply and that it is grounded. Finally, check the burner assembly, the flame rod, and the gas valve assembly for issues.

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Error Code E015 – Abnormal Control Board

Error code E015 indicates a damaged control board. To check your control board, ensure it is receiving the proper amount of power and check the ground fault circuit for issues. If you do need to replace your control board, ensure the one you are purchasing matches your water heater.

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Error Code E016 – Heat Exchanger Is Overheating

Error code E016 indicates that the heat exchanger is overheating. To resolve this, turn off your water heater for at least 30 minutes and restart it. If that does not resolve your issue, remove and clean the inlet water strainer.

You should also check the automatic flow adjustment valve and flush the heat exchanger to remove any mineral buildup. You may also need to replace your High-Temperature Limiter if it is not reading in the correct range.

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Error Code E021 or E022 – Cold Water Inlet Thermistor

Both error codes E021 and E022 indicate a problem with the thermistor. To resolve this, remove the connectors from the PCB board and check the resistance between the CN13 wires. If the resistance falls between 0.8 to 20k Ohm, then check the connection. If it falls out of this range, replace the thermistor.

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Error Code E027 – Air Pressure Sensor Abnormal Activity

Error Code E027 indicates some type of airflow issue. You should inspect your vent pipe for obstructions and clean the air filter as well. If you are still having issues, you may have to replace the Air Pressure Sensor or control board.

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Error Code E028 – Water Leak

Error code E028 indicates a water leak. To resolve this, check the pipeline for a leak and replace the O-rings. You should also do a manual reset of your system to see if this resolves your issues.

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Error Code E030 – Exhaust Overheat

Error code E030 indicates an exhaust overheat. To resolve this, turn off the water heater for thirty minutes and then restart it. If that doesn’t work, remove and clean the inlet water strainer and check the automatic flow adjustment valve. Finally, consider flushing your water heater.

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Error Code E032 or E033 – Cold Water Inlet Thermistor

Both error codes E032 and E033 indicate a problem with your thermistor. To resolve this, remove the connectors from the PCB board and check the resistance between the CN13 wires. If the resistance falls between 0.8 to 20k Ohm, then check the connection. If it falls out of this range, replace the thermistor.

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Error Code E034 – Flow Adjustment Valve Abnormal

Error code E034 indicates an issue with the flow adjustment valve. You should check your flow adjustment valve and replace it if necessary.

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Error Code E035 – Gas Pressure Sensor Indicating Abnormal Activity

Error code E035 indicates an issue with the gas pressure sensor. To resolve this, check the gas line and check the voltage of the CN7. If the voltage is not between 0.2 to 0.6VDC, then you will need to replace the Gas Pressure Sensor.

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Error Code E036 – Communication Failure

Error code E036 indicates a communication failure. Communication failures will have to be resolved by a professional.

Error Code E037 – Water Leak

Error code E037 indicates a water leak inside your water heater. To resolve this, you will need to close the cold-water valve and inspect the tankless unit. If you can identify which component is leaking, repair or replace it. If your water leakage detector is not working properly, you may also need to replace it as well.

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Error Code E038 – Circulation Pump

Error code E038 indicates a circulation pump issue. You should check the circulation pump and water flow sensor for issues. You should also check the cold water main.

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Error Code E039 – Water Flow Sensor

Error code E039 indicates a water flow sensor issue. You should check and replace the water flow sensor to resolve this error code.

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Error Code E041 – Hot Water Outlet Thermistor 2

Error code E041 indicates the hot water outlet thermistor 2 is in the open position. You should check the thermistor and replace it to resolve this error code.

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Error Code E042 – Hot Water Outlet Thermistor 2

Error code E042 indicates that the hot water outlet thermistor 2 has a shortage in the system. To resolve this, check the thermistor and thermistor connection and replace them if necessary.

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Error Code E043 – Cascade Connection

Error code E043 indicates a communications cable due to an abnormal cascade connection. You should check your model type and replace the communications cable to resolve this error code.

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Error Code E044 – Thermistor Connection

Error code E044 indicates a thermistor connection issue. You should check the thermistor and the thermistor connection and replace them if necessary.

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Error Code E045 – Mixing Valve

Error code E045 indicates an issue with the mixing valve. You should check the mixing valve and replace it if necessary. You should also check the mixing valve transformer and replace it if necessary.

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Error Code E046 – Limit Control

Error code E046 indicates an issue with the unit’s high-limit switch. You will need to contact a professional to help you resolve this issue.

Error Code E047 – Exhaust Thermostat

Error code E047 indicates an issue with the exhaust thermostat. You will need to contact a professional to help you resolve this issue.

Error Code E048 – LPG Gas Pressure

Error code E048 indicates an issue with the LPG Gas Pressure. You should check the LPG gas and pressure-reducing valve for issues and add LPG gas if necessary. You should inspect the gas pressure flow sensor and replace it if it is not functioning properly.

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Error Code E060 – Dual Venuri

Error code E060 indicates an issue with the dual venturi. You should first try rebooting your water heater and unplugging it for at least five minutes. If you still receive an error code after rebooting, you will need to replace your dual venuri.

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Error Code E109 – Fan Motor

Error code E109 indicates an issue with the fan motor. You should clean the intake air filter and reboot your system by unplugging it for at least five minutes. If this does not resolve your issue, you will need to replace your fan motor.

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Error Code E110 – Airflow

Error code E110 indicates an airflow issue. You should inspect your unit’s exhaust pipe and remove any obstructions you find there. You should also clean the air filter intake and replace the air pressure sensor if it isn’t working properly.

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Error Code E407 – Thermistor

Error code E0407 indicates a thermistor issue. You should check the thermistor and the thermistor connection and replace them if necessary.

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Error Code E421 – Thermistor

Error code E0421 indicates a thermistor issue. You should check the thermistor and the thermistor connection and replace them if necessary.

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Error Code E432 – Thermistor

Error code E0421 indicates a thermistor issue. You should check the thermistor and the thermistor connection and replace them if necessary.

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Error Code E434 – Water Adjustment Valve

Error code E434 indicates an issue with the water adjustment valve. To resolve this, inspect the water adjustment valve and replace it if necessary.

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Error Code E438 – Circulation Pump

Error code E438 indicates an issue with the circulation pump. You should check that all of the water supply and return lines are fully open and that the 2-way valve is set in the right direction. If necessary, check the model number of your water heater and replace the circulation pump.

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Error Code E439 – Flow Sensor

Error code E439 indicates an issue with the flow sensor. You should check your water supply and flow and inspect the flow sensor for issues. If your flow sensor is broken, you should replace it with a new one.

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Error Code E441 – Thermistor

Error code E0421 indicates a thermistor issue. You should check the thermistor and the thermistor connection and replace them if necessary.

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Error Code E445 – Bypass Mixing Valve

Error code E445 indicates an issue with the bypass mixing valve. You should replace the mixing valve or the PCB main board to resolve your issue.

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Error Code E480 – External Tank Thermistor

Error code E480 indicates an issue with the external tank thermistor. You should inspect the thermistor connection and replace it if it is not working properly.

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Error Code E515 – PCB Board

Error code E515 indicates an issue with the PCB board. You can resolve this issue by unplugging your unit and try using a different outlet. You should also inspect the PCB board and igniter for any issues. The fan, Dual Venturi, and 3-way valve connection should also be inspected for issues.

If you are unable to resolve your issue, you will need to replace the PCB board completely.

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Error Code E517 – Dip Switch

Error code E517 indicates an issue with the dip switch. You should check that the dip switch settings are correct for the front panel and PCB board.

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Error Code E593 – Front Panel Key

Error code E593 indicates an issue with the front panel key. You can resolve this issue by unplugging your water heater for at least five minutes. If this does not resolve your issue, the front panel should be replaced.

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Error Code E594 – Communication Error

Error code E594 indicates a communication error. You should inspect the PCB board for any wiring issues. If your PCB board is damaged, you will need to replace it.

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Error Code E615 – Input And Memory

Error code E615 indicates an issue with input and memory. You should reset your water heater by unplugging it for at least five minutes. If this does not resolve your issue, you should check and replace the PCB board or Air Pressure Sensor.

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Error Code E736 – Cascade Communication

Error code E736 indicates an issue with the cascade communication. You will need to inspect the PBC board and the cascade communication cable for issues. Replace the cascade communication table if you keep having issues.

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Error Code E740 – Outdoor Sensor

Error code E740 indicates an issue with the outdoor temperature sensor. Inspect the PCB board to ensure the sensor connection is securely in place. If the outdoor sensor is damaged, you will need to replace it.

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Error Code E760 – Flushing/Service Alarm

Error code E760 is an alert that it is time to flush the scale and lime buildup from your water heater. You should descale the tank yourself or hire a professional to do it for you.

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Error Code E782 – Main Panel Communication

Error code E782 indicates an issue with the main panel communication. You should inspect the PCB board and replace it if you are having issues.

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Error Code E783 – OT Remote Controller

Error code E783 indicates an issue with the OT Remote Controller. You should check the wiring in your remote control and reboot it by unplugging it for at least five minutes. A certified technician can offer more information on how to resolve these issues.

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Error Code E787 – Flow Switch

Error code E787 indicates an issue with the flow switch. To resolve this issue, you should ensure the supply water line is supplying water to the tankless. If the flow switch is damaged, replace the flow switch.

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How Do I Reset My Navien Tankless Water Heater?

To reset your Navien tankless water heater, simply unplug it from the power source for at least five minutes and then plug it back in. This will initiate the restart process and clear error codes that you may have resolved.

Finally, if you are still having issues, you should consider contacting a professional to offer assistance with your problem.

Call A Professional If You Need Help

You should contact a professional if you need help clearing your error code. Some error codes indicate an issue that you may not be able to resolve easily. You should always consult a professional before dealing with complex electrical components or gas valves.

Conclusion

Whether you are installing your water heater or have had it for a while, Navien error codes are beneficial for identifying and addressing issues with your water heater. You can use the list of error codes above to make problem-solving easier. If you receive an error code on your Navien water heater, it is important that you identify the cause of it so you can resolve it properly.

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