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Navien Error Codes

If your Navien tankless water heater is displaying an error code, you may be able to solve the problem yourself. Check the error code and see if it’s something you can handle before calling a professional. For your convenience, we’ve included links to many of the replacement parts.

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Error Codes for Navien Tankless Water Heaters

Although this article covers the error codes for Navien tankless water heaters, we highly recommend checking your owners manual for specific information on your model. Over time manufacturers make changes to their product lines, and your owners manual is always your best resource.

Error Codes for Navien Tankless Water Heaters


Important:
We highly recommend contacting a licensed professional to troubleshoot and diagnose any issues with your tankless water heater. They’ll not only have the knowledge and experience necessary to fix your tankless, but they’ll also have access to the proper tools and parts.

Error Code E001

Boiling Water in Heat Exchanger

An Error Code E001 indicates that the water inside the heat exchanger is boiling. 

  • Clean the water inlet filter
  • Check the water adjustment valve
  • Inspect and flush the heat exchanger
  • Check the PCB board. If faulty it will need to be replaced. Be sure to replace it with the right one for your model.

Available Parts:

Error Code E002

Low Water Pressure

When your Navien appliance experiences low water pressure, it’ll display an Error Code E002.

The good news is, once the water pressure increases the unit will automatically reset itself. No further action will be necessary.

Error Code E003

Ignition Failure

If your Navien tankless experiences ignition failure it’ll display an Error Code E003. 

  • Check the main gas supply. The supply valve should be open. We highly recommend calling a professional to do any additional troubleshooting when working with gas
  • Check that the power is ON
  • Check that the igniter sparks. Replace the flame rod assembly if needed

Available Parts:

Error Code 004

False Flame Detection

An Error Code 004 indicates a false flame detection. 

  • Check the power cord to verify that it is properly grounded. It’s possible that the ground wire is not connected
  • Check that the igniter delivers a spark
  • Replace the Flame Rod Assembly if needed

Available Parts:

Error Code E007 & E008

Faulty Thermistor

Both Error Code E007 and E008 are related to the thermistor. 

  • Remove the connector from the PCB before measuring the resistance of the thermistor
  • If the resistance between the 2 red wires of CN13 is from 0.8 to 20k ohm at normal condition, your thermistor is fine and you should check the connector
  • If the resistance does not fall within the above normal range, you’ll need to replace the thermistor.

Available Parts:

Error Code E009

Abnormal Fan Motor Activity

An Error Code E009 is an indication that your fan motor is not operating as it should. 

  • Check and clean the air filter
  • Check and clean the fan motor
  • If the fan has enough nominal operation voltage, yet it pulses, you’ll need to replace the fan

Available Parts:

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Error Code E010

Abnormal Air Pressure

An Error Code E010 indicates a venting issue. 

  • Check the vent pipe and remove any obstructions
  • Remove and clean the air filter
  • The problem could be with the Air Pressure Flow Sensor (APS). If this is the problem, it may need to be replaced
  • If you are unable to locate the problem yourself, you should call for service as soon as possible.

Error Code E011

High Water Pressure

An Error Code E011 indicates that the water pressure sensor is detecting high water pressure. 

  • Check the water pressure sensor
  • If it does not automatically reset, you may need to replace the sensor

Available Parts:

Error Code E012

Flame Loss

There are a number of things that could cause your Navien Tankless Water Heater to throw an Error Code E012. 

  • Check the main gas line. The valve should be fully open
  • Check that there are no obstructions in the intake air pipe
  • Check that the unit is connected properly to the power supply and that it’s grounded
  • If your tankless has sufficient gas pressure, check the burner assembly, the flame rod, and the gas valve assembly

Available Parts:

Error Code E015

Abnormal Control Board

An Error Code E015 could indicate that the control board needs to be replaced. 

  • Check the power supply
  • Check the ground fault circuit (GFI)
  • If you do need to replace the PCB Board, there are several different ones. Be sure to check your Owners Manual to ensure you order the correct board

Available Parts:

Error Code E016

Heat Exchanger is Overheating

Your heat exchanger is overheating if your Navien is displaying an Error Code E016. 

  • Turn off your tankless appliance for a minimum of 30-minutes. Then restart
  • Remove and clean the inlet water strainer
  • Check the automatic flow adjustment valve
  • Flush the heat exchanger to remove limescale build-up
  • At least 30 minutes after the error code, you can take an ohm reading on the High Temperature Limiter. If the reading is not within the normal range, you’ll need to replace the High Temperature Limiter. If it is within the normal range, you’ll need to replace the PCB Board

Available Parts:

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Error Code E021 or E022

Cold Water Inlet Thermistor

If you see an Error Code E021 or E022, you have a problem with your Thermistor. 

  • You’ll need to remove the connectors from the PCB Board and check the resistance between the two black wires of CN13
  • Normal resistance is: 0.8 to 20k Ohm.  If your results fall into this range, check the connection
  • If the results fall outside of this range, you’ll need to replace the thermistor

Available Parts:

Error Code E027

Air Pressure Sensor Abnormal Activity

When you see an E027 Error Code, you have some sort of air flow issue. The problem could be as simple as an obstruction, but it could also require replacing a sensor or control board. 

  • Inspect your vent pipe. There may just be an obstruction that is interfering with the air flow
  • Remove and clean the air filter
  • If you’re comfortable measuring electrical resistance, you can check the voltage on the fan motor. But we recommend hiring a professional if the above two steps didn’t solve the problem
  • It’s likely you’ll need to replace the Air Pressure Sensor or the control board

Available Parts:

Error Code E028

Water Leak

If the pipe line has a water leak your Navien will display an Error Code E028.

  • Check the pipe line for a leak
  • Check and replace the O-Rings
  • Do a manual reset

Available Parts:

Error Code E030

Exhaust Overheat

If your Navien tankless displays an Error Code E030 a high limit switch has shut down the appliance. This happens when the flue temperature reaches a temperature above 149°F.

  • Turn off the water heater for a minimum of 30-minutes. Then restart
  • Remove and clean the inlet water strainer
  • Check the automatic flow adjustment valve
  • Flush the tankless water heater

Available Parts:

Error Code E032 or E033

Cold Water Inlet Thermistor

If your appliance is displaying either an E032 or E033 Error Code you have a problem with your thermistor.

  • You’ll need to remove the connectors from the PC Board and check the resistance between the two black wires of CN13
  • Normal resistance is: 0.8 to 20k Ohm.  If your results fall into this range, check the connection
  • If the results fall outside of this range, you’ll need to replace the thermistor

Available Parts:

Error Code E034

Flow Adjustment Valve Abnormal

If you receive an Error Code E034 your unit there’s an abnormality with the flow adjustment valve.

  • You need to check the flow adjustment valve, if necessary, you can replace the valve

Available Parts:

Error Code E035

Gas Pressure Sensor Indicating Abnormal Activity

If you see an Error Code E035 there’s abnormal activity of the gas pressure sensor.

  • Check the gas line
  • With the gas valve ON, check the voltage between the black and white wire of CN7. It should be 0.2 – 0.6VDC. If it is not, replace the Gas Pressure Sensor
  • If it is within this range, check the voltage between the black and white wire of CN7 with the gas valve OFF. It should be 1 – 4VDC. If it is not, replace the Gas Pressure Sensor
  • If it is, check the gas connector

Available Parts:

Error Code E036

Communication Failure

An Error Code E036 indicates a communication failure.

Please contact a professional to resolve this issue.

Error Code E037

Water Leak

An Error Code E037 indicates that there’s a water leak inside the water heater.

  • Close the cold water main
  • Open the tankless unit. If there is a leaking part, it’ll need to be replaced. The problem could also be as simple are replacing an O-Ring
  • Check the water leakage detector. If it’s operating, check the connector
  • If it’s not operating, you’ll need to replace the water leakage detector

Available Parts:

Error Code E038

Circulation Pump

If you’re seeing an Error Code E038, there’s an abnormality occurring with the circulation pump.

  • Check the circulation pump
  • Check the water flow sensor
  • Check the cold water main

Available Parts:

Error Code E039

Water Flow Sensor

An abnormal water flow sensor is indicated by an Error Code E039.

  • Check the water flow sensor
  • Replace the water flow sensor

Available Parts:

Error Code E041

Hot Water Outlet Thermistor 2

An Error Code E041 indicates the hot water outlet thermistor 2 is open.

  • Check thermistor
  • Replace thermistor

Available Parts:

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Error Code E042

Hot Water Outlet Thermistor 2

An Error Code E042 indicates that the hot water outlet thermistor 2 has a short.

  • Check thermistor
  • Confirm the thermistor connection
  • Replace thermistor

Available Parts:

Error Code E043

Cascade Connection

An Error Code E043 indicates that there may be an issue with the communications cable due to an abnormal cascade connection.

  • Check your model type
  • Check your communications cable

Available Parts:

Error Code E044

Thermistor Connection

An Error Code E044 indicates that the thermistor is either improperly connected or it needs to be replaced.

  • Check the thermistor
  • Check the thermistor connection
  • Replace the thermistor

Available Parts:

Error Code E045

Mixing Valve

An Error Code E045 indicates there’s something abnormal occurring with the mixing valve.

  • Check the mixing valve, replace if necessary
  • Check the mixing valve transformer, replace if necessary

Available Parts:

Error Code E046

Limit Control

An Error Code E046 indicates that there’s an issue with the unit’s high limit switch.

We highly recommend contacting a professional plumber to repair your unit or call Navien technical support at 1(800) 519-8794.

Error Code E047

Exhaust Thermostat

An Error Code E047 indicates an abnormality with the exhaust thermostat.

We highly recommend contacting a professional plumber to repair your unit or call Navien technical support at 1(800) 519-8794.

Error Code E048

LPG Gas Pressure

An Error Code E048 indicates an abnormality with the LPG gas pressure.

  • Check the LPG gas and pressure reducing valve
  • Add LPG gas if needed
  • Inspect the gas pressure flow sensor
  • Replace the gas pressure flow sensor
  • Contact a professional plumber to repair your unit or call Navien technical support at 1(800) 519-8794

Available Parts:

Error Code E060

Dual Venuri

If your tankless unit throws an Error Code E060, it’s an indication that there’s an abnormality in the Dual Venturi.

  • First, try rebooting the system by unplugging your tankless. Wait 2 to 3 minutes and then plug it back in
  • If it still throws an E060 error code, then the Dual Venturi will need to be replaced. Be sure to check your model number before ordering parts

Available Parts:

Error Code E109

Fan Motor

An Error Code E109 indicates that the fan motor is not properly operating.

  • Clean the intake air filter
  • Reboot the system by unplugging your tankless. Wait 2 to 3 minutes and then plug it back in
  • Check your model and replace the fan motor

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Error Code E110

Air Flow

An Error Code E110 indicates that there’s an issue with the air flow to your tankless.

  • Inspect your unit’s exhaust pipe. Remove any obstructions if needed
  • Clean the air filter intake
  • Check and/or replace the air pressure sensor

Available Parts:

Error Code E407

Thermistor

The thermistor for the hot water outlet is either open or is short circuited if you see an Error Code E407.

  • Inspect the thermistor
  • Check that the thermistor is making a good connection
  • Replace thermistor

Available Parts:

Error Code E421

Thermistor

An Error Code E421 indicates the cold water inlet 1 thermistor is open or short circuited.

  • Inspect the thermistor
  • Check that the thermistor is making a good connection
  • Replace the thermistor

Available Parts:  

Error Code E432

Thermistor

An Error Code E432 indicates the cold water inlet 2 thermistor is open or short circuited.

  • Inspect the thermistor
  • Check that the thermistor is making a good connection
  • Replace the thermistor

Available Parts:

Error Code E434

Water Adjustment Valve

Your unit’s water adjustment valve is not properly operating if you see an Error Code E434.

  • Inspect the water adjustment valve
  • Ensure the adjustment valve is making a good connection
  • Replace the water adjustment valve. Be sure to check your model to order the right part

Available Parts:

Error Code E438

Circulation Pump

An Error Code E438 indicates that the circulation pump is not properly functioning.

  • Outside Your Unit: Check that all of the water supply and return lines are fully open
  • Inside Your Unit: Check that the 2-way valve is set in the right direction
  • Check your model number and replace the circulation pump if necessary

Available Parts:

Error Code E439

Flow Sensor

If your Navien Tankless is throwing an Error Code E439 there’s an abnormality with the flow sensor.

  • Check your water supply and flow
  • Inspect the flow sensor
  • Ensure the flow sensor wire is connected properly to the control board
  • Remove the flow sensor. Clean/descale the turbine
  • Replace the flow sensor

Available Parts:

Error Code E441

Thermistor

An Error Code E441 indicates that the hot water inlet 2 thermistor is either open or shorted.

  • Inspect the thermistor
  • Check that the thermistor is connected properly
  • Install a new thermistor

Available Parts

Error Code E445

Bypass Mixing Valve

An Error Code E445 indicates the bypass mixing valve is not properly operating.

  • The mixing valve sensor may be faulty
  • Ensure the wiring and connection to the main board is correct
  • Inspect the valve to ensure it isn’t damaged or blocked
  • Replace the mixing valve
  • Replace the PCB main board (check your model number before ordering)

Available Parts:

Error Code E480

External Tank Thermistor

An Error Code E480 is an indication that the external tank thermistor is either open or shorted.

  • Inspect the thermistor connection and wire
  • Check that the connection is not wet. This could cause a short
  • Replace the thermistor 

Available Parts

Error Code E515

PCB Board

There is an abnormal operation with the PCB board if you see an Error Code E515.

  • Unplug your unit and try using a different outlet
  • Check that your electrical cord is grounded properly
  • Inspect the PCB board
  • Inspect the igniter and connection
  • Inspect the fan and connection
  • Inspect the Dual Venturi and connection
  • Inspect the 3-way valve and connection
  • Check your model number and replace the PCB board if needed

Available Parts:

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Error Code E517

Dip Switch 

An Error Code E517 indicated an issue with the DIP switch.

  • Check that the dip switch settings are correct
  • Check the front panel dip switch settings
  • Check the PCB board dip switch settings 

Available Parts

Error Code E593

Front Panel Key

An Error Code E593 indicates there is either a front panel display or a key issue.

  • Reboot the system by unplugging your tankless. Wait 2 to 3 minutes and then plug it back in
  • If you continue to see the error, the front panel should be replaced

Available Parts:

Error Code E594

Communication Error

An Error Code E594 indicates a communication or partial communication error.

  • Inspect the PCB board
  • Check the wiring and connections from the major components to the PCB board
  • Pay special attention to the connections of the flame rod, pressure sensor and exhaust sensor
  • Check your model and replace the PCB board

Available Parts:

Error Code E615

Input and Memory

An Error Code E615 is an indication that there’s an issue with the input and memory.

  • Reboot the system by unplugging your tankless. Wait 2 to 3 minutes and then plug it back in
  • Check the PCB board wiring and connection
  • Test the pressure sensor output voltage
  • Replace the PCB board
  • Replace the pressure sensor 

Available Parts:

Error Code E736

Cascade Communication

Your Navien tankless has an issue with the cascade communication if you see an Error Code E736.

  • Inspect your PCB board. Ensure that the PCB is compatible with the cascade communication cable
  • Inspect the cascade cable connection to the PCB board
  • Check the cascade settings
  • Reboot the system by unplugging your tankless. Wait 2 to 3 minutes and then plug it back in
  • If the tankless continues to display an error code E736 replace the cascade cable

Available Parts

Error Code E740

Outdoor Sensor

An Error Code E740 indicates there’s an issue with the outdoor temperature sensor.

  • Inspect the PCB board to ensure the sensor connection is securely in place 
  • Inspect the wire that runs from the tankless system to the outdoor sensor for damage
  • If the above looks good, you can try bringing the outdoor sensor inside for 24 hours. This will allow it to dry out and may resolve the issue
  • Replace the outdoor sensor

Available Parts:

Error Code E760

Flushing/Service Alarm

An Error Code E760 is alerting you that it’s time to flush the scale and lime build-up from your tankless.

Available Parts:

Error Code E782

Main Panel Communication

An Error Code E782 indicates that there’s a communication issue with the main panel.

  • Inspect the PCB board. Check the connection and look for signs of water
  • Although it may be necessary to replace the PCB board, it is a good idea to call Navien technical support (800-519-8794) or a professional plumber 
  • If you choose to replace the PCB board, be sure to check your model number before ordering

Available Parts

Error Code E783

OT Remote Controller

An Error Code E783 indicates an issue with the OT remote controller

  • Check the wiring in the remote control
  • Reboot the system by unplugging your tankless. Wait 2 to 3 minutes and then plug it back in
  • If you still receive an E783 Error Code, you can either contact Navien technical support (800-519-8794) or replace the remote control

Available Parts:

Error Code E787

Flow Switch

The external flow switch is causing an Error Code E787.

  • Ensure that the supply water line is supplying water to the tankless
  • Check that the flow switch position is either in the on or off position
  • Replace the flow switch

Available Parts:

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