How to fix Navien E003 code: Ignition failure error easily

Learn the reasons which cause error E003 on Navien tankless water heater and find a straightforward fix to make it work again.

In this quick tutorial, you will learn the reasons that cause the Navien error code E003 on tankless water heaters and a simple way to troubleshoot and find an easy fix that can solve the issue and save your hard-earned money.

What is Error code E003 on the Navien tankless heater?

navien e003 error code in user manual

When you look at the Navien manufacturer User’s Information manual, there is an error codes chart from which you can see error code E003 is for Ignition failure. On hot water demand, a gas tankless water heater should first turn on the gas and ignite the flame to heat the water at high temperatures. When no flame is ignited due to some technical issues, the water won’t get hot, gives cold water, or sometimes shuts down and shows error E003 on the front panel display.

Reasons that cause E003 error code in Navien heaters

According to the user’s information manual, this error is caused when the gas supply is off. Yes, of course, it is one reason, but there are a few other reasons that cause this error code, which are listed below.

  • Gas supply turned off or No gas in gas cylinder
  • Blockages in the air intake filter
  • Flame rod/ Ignitor wiring damaged
  • Flame rod/Igniter damaged

Fixing Navien Tankless Water Heater Code E003

Follow the below easy and straightforward steps to clear E003 error code and get your hot water back. These fixes works on all NPE and NCB units like Navien NPE 240 A2, NCB 240 and other capacities also.

Gas supply turned off or No gas in gas cylinder

While performing maintenance or something, you might have turned off the gas supply to the heater and forgot to turn it on, partially turned the valve, or the gas in the cylinder or supply is completed or stopped. All these cases don’t allow the required gas flow to the heater, which ends up in no ignition and no hot water and pop-out error codes.

How to Fix:

  • Check the gas valve and turn it completely on.
  • Check the gas source or cylinder weither it has enough gas to supply the heater.
  • If needed connect a manometer to the pressure port, and check the inlet gas pressure.

Blockages in the air intake filter

Insects and debris flying in the air enter the air intake pipe. They are stopped near the air intake filter to prevent them from entering the heater unit. This debris and insects like flies, wasps, and dirt get stuck to the air filter and block the air intake. Combustion in the heat exchanger doesn’t happen correctly when fresh air intake is adequate, which is a problem, so the navien heater shows error code E003.

How to Fix:

To clean the air filter, turn off the heater and remove the front panel using a screwdriver, or some units have just clips that we can remove easily without any tool. Locate the air intake filter, which is at the top left. Unscrew it, look for any debris and dirt, clean it with a toothbrush, and fix it again.

how to remove air intake filter on navien tankless water heater

After placing it back, turn on the heater and check for the error code. If you still get code E003, you should look directly at the flame rod/Ignitor spark.

Flame rod/ Ignitor wiring damaged

The Flame rod/Ignitor is a component in gas heaters placed near the gas burners. The flame rod is made of conductive metals to create a spark to ignite the gas. The flame rod can also sense whether the flame is on or off and send the signal to the controller PCB through wires. If these wires are damaged or broken, the controller PCB cannot sense the signal and pops error code E003 on the front panel display.

flame rod of navien tankless water heater location

Generally, in navien tankless water heaters, the flame rod is located on the front of the heat exchanger, which is easy to access, but in a few older models, it is on the side of the heat exchanger. We need to remove the blower connected with three screws to access the flame rod by twisting the blower outwards.

How to Fix:

  • Locate the flame rod and investigate the wires connected between the flame rod and the control board PCB.
  • If the wires are faulty or broken, replace those wires. If they look good, once try to remove them and connect again. If still no luck, follow the next step.

Flame rod/Ignitor damaged.

After many years of usage, the flame rod gets dirty and damaged, which needs to be replaced. Take the flame rod out and check its current situation. If it is damaged, check for the part number on the flame rod or in the manual of your heater model and purchase the new flame rod.

Navien good and bad flamerods representation

How to Fix:

Follow the below steps to replace the flame rod in Navien tankless heater.

  • Turn off the heater and close the gas supply to the heater.
  • Remove the front panel to access the flame rod.
  • Remove three wires connected to the flame rod and put some marks on them so that it will be easy to remember while putting them back on the new flame rod.
  • Unscrew the flame rod and pull it out.
  • Put the new flame rod inside the ignitor slot and tighten the screws.
  • Connect the three wires to the new flame rod and cover them with rubber insulating caps.
  • That’s it flame rod replacement is done.

Put back the front panel, turn on the heater, and reset it by pressing the reset button. The heater restarts and doesn’t show any error code. Set the temperature to maximum and check in faucets for hot water.

If you are thinking of performing full water heater cleanup, we have

If you get other errors on your Navien hot water heater look into our comprehensive guide on Navien tankless water heater error codes.

If you are experiencing E110 code you can refer our dedicated article on How to Fix Navien code E110

If you have any questions or concerns, don’t hesitate to comment below! Our team is here to assist you and provide all the necessary information. Your feedback is important to us, so please feel free to share your thoughts, and we’ll respond as soon as possible.

TanklessHelp Staff

TanklessHelp Staff has an experienced writers and researchers in the field of water heating technology. With a background in HVAC and plumbing, Tanklesshelp staff has in-depth knowledge in many types of waterheaters in America and Canada. They have a passion for educating homeowners and businesses on solving easy to hard repairs and guide them on how to maintain them to save money.

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  1. Thank you! This worked. My non-mechanical 18 year old followed the directions and cleaned the air intake filter. This mom says thank you.

  2. I have a Navien NPE-240S NG tankless heater with E.003 error code and producing no hot water. Your page describes how to resolve this issue, but does not seem to match what I find on my unit. There is a short cylindrical pipe on the bottom of my unit that is capped by a dual-pin clip. I removed this clip, pulled off the cap. This released about a cup of water and brown sludge. I cleaned it up, put it back together, powered the unit back up and the E.003 is gone and the unit is producing hot water normally.

    What is the name and function of the feature I cleaned?

    Do you have documentation for the NPE-240S NG available?

  3. We have 2, Navien NR-240A water heaters.. WE were gone to AZ for 4 months, the heaters are taking forever to give us hot water on demand. The covers are off and showing an E003 error code, which I guess is the ignition failure. We can reset the circuit breaker and it seems to work for a short time, then stops again.. no

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