Navien Tankless Water Heater Ignition Failure [How To Fix]

The Navien E003 error code indicates ignition failure. I’ve talked with Navien customer support about this issue and fixed this error code in many heaters. The main reasons behind the Navien tankless water heater ignition failure and E003 error code are:

  • Power failure.
  • Dirty air intake filter.
  • Poor gas supply.
  • Flame rod issues.
  • Faulty PCB.
  • And more.

I’ll talk about all these issues in detail along with their appropriate fixes in this guide. You’ll also learn how to replace the flame rod assembly and PCB properly. So, let’s dive in!

navien tankless water heater ignition failure

There are a variety of reasons that could lead to the ignition failure issue in Navien water heaters. I’ll take a look at the most common culprits behind this problem in this section.

01. Power Failure

If the heater doesn’t get proper power, it can lead to ignition failure. It often happens with Navien units. If you’ve only used your heater for a short period, there should be no major problem with your water heater. So, it’s likely that the ignition failure is a result of power failure in such cases.

How To Fix:

First, make sure that the plug of the water heater is connected properly to the power outlet. If it’s loose, tighten it before you do anything else.

If the plug was connected properly in the first place, you can fix this issue by simply resetting the water heater. It’s not hard to reset a Navien water heater. You’ll find the reset button on the keypad of the heater. Just press it and the unit will be reset.

reset button of navien tankless water heater

You can also power cycle the heater. Unplug the heater from the power outlet and reconnect it after a while. Doing any of these two things should be enough to remove the error code if it had come up due to a glitch.

However, there’s the possibility that the issue will still remain. In that case, things have gotten a little more serious. Keep on reading to find out more about these potential issues and their solutions.

Before moving to the other potential problems, remember that you can contact Navien tech support if your unit is still under warranty. The stipulation by Navien when making a warranty claim is that the service provider has to call Navien support while working on the job.

From their end, they’ll confirm the root cause of the issue with the service provider. If any replacement part is needed, they’ll provide it. You’ll have to make the claim by phone and call navien at this number: 800-519-8794.

The available times to reach out to them are:

  • Mon-Fri: 5 am-6 pm PST
  • Sat-Sun: 5 am-5 pm PST

However, you can keep on reading if your unit is past warranty. In those situations, you’re on your own to fix the issue. But don’t worry, I’ll help you as much as I can to get to the main reason behind the problem.

02. Dirty Air Intake Filter

I’ll try to keep this guide as simple as possible by discussing the problems that are easy to fix first. On that note, the first thing you should check after trying to reset the heater is the air intake filter.

dirty air intake filter of navien tankless water heater

The Navien heater draws air through that filter. If the filter gets dirty, it won’t be able to suck in the required amount of air for proper combustion. The end result is that the air to fuel ratio will be messed up.

At times, even insects like ants and wasps can get into the air filter and block the airflow. When the situation gets too bad, it’s possible that the heater will go into ignition failure mode. That’s when the E003 error code will pop up on the display of your heater.

How To Fix:

The air intake filter gets dirty from time to time. So, there’s no need to be concerned if that’s happened with your air filter. First, you’ll have to remove the air intake filter and inspect its condition.

If the air intake filter turns out to be dirty, then you’d have to remove it and clean it. If you need more details on how to do it properly, I’ve broken down the process into simple steps. Here they are:

  1. Unplug the water heater and make sure that the heater has no power. Then, remove the outer cover of the heater.
  2. Locate the air intake filter by looking at the top of the water heater. It’ll be placed right under the combustion air intake. You’ll see a set screw that holds the air intake filter securely in its place.
  3. Remove that screw and you should be able to pull out the air filter easily. Now, it’s time to inspect its condition. If it’s too dirty, you may have just found the culprit behind the ignition failure issue.
  4. Even if it’s not entirely dirty, you should clean it. You’ll be able to put out most of the dirt in the filter by yourself. But I recommend rinsing the filter in running water to do a good job of cleaning it.
  5. After getting the dirt out of the filter, put the filter back in its place and tighten the set screw to secure it in place.

That’s how easy it is to clean the air filter. Once you’re done with all the steps above, plug in the power connection of the heater and turn it back on. Hopefully, the error code will go away and the heater will run. But if the error code persists, keep on reading to find the real problem and solve it.

03. Poor Gas Supply

The most common singular reason behind the Navien ignition failure issue is improper gas supply. It shouldn’t come off as a surprise to you. A water heater needs fuel to operate. So, if there are issues with the gas supply, it’s obvious that the heater won’t ignite properly.

gas supply issues of navien tankless water heater

The first thing you should look into when you’re inspecting a gas supply issue is whether you have a gas supply in your home. Sometimes, people forget to pay their utility bills on time and the entire gas supply gets cut off.

It’s not a hard thing to check. Just turn on another gas powered appliance in your house and see if it’s running. If none of the gas powered devices working, that means the gas supply has been cut off. But if the gas powered components are working, you can rest assured that gas is flowing to your house.

The next thing you should check is the main gas valve. Remember that it should be completely parallel to the gas lines. If it’s perpendicular or not even fully parallel, that means the unit isn’t getting sufficient gas supply.

If that’s good too, the final thing I can think of here is to check the gas lines. First of all, make sure that the gas lines are the right size as per the guidelines in your owner’s manual.

If the size of the gas line checks out, check for dirt or obstruction in the gas lines. It’s possible that dirt and debris in the gas lines can restrict the flow of gas. So, there will be less gas than required for proper combustion. It can lead to ignition failure and pop up the E003 error code.

How To Fix:

If there’s no gas supply to your entire house, contact your local utility company. Clear your dues if you have any outstanding bills to solve the issue. If the gas supply was cut off due to any temporary issue, ask them when you can expect it. You have no option but to keep calm and wait for it to get fixed.

If the main gas supply isn’t fully parallel to the gas lines, turn it so that you can get it as parallel to the gas lines as possible. See if that fixes the issue and whether the heater runs properly now.

The final possible culprit here is using gas lines of the wrong size or clogged gas lines. In both these cases, you should replace the gas line. Make sure you follow the requirements in your owner’s manual. Hopefully, doing these things will solve the gas supply issue and your heater will operate nicely.

04. Flame Rod Issues

Another common reason behind the Navien E003 ignition failure error code is flame rod issues. The flame rod assembly is the most important component when it comes to igniting the heater. That’s because the flame rods have two very important jobs.

flame rods of navien tankless water heater

Firstly, it acts as an igniter by producing sparks when the heater needs to turn on. You can see the flame rod through the little window once you remove the front cover. Check if it’s producing a spark when you turn the water heater on. 

If there’s no spark, there’s a good chance that the flame rod has gone bad. The ignition wiring could have also gone bad and caused this issue as it also communicates with the PCB. If the wiring is faulty, it won’t be able to signal the PCB about producing the spark.

Secondly, there’s a flame rod wire connected to the flame rods. Its main job is to sense the flame and communicate that to the PCB. Due to this signal, the PCB keeps feeding gas to the water heater. If the wire was faulty, the gas supply would be stopped and your heater won’t ignite.

The flame rods are also prone to going bad with time. As you keep using them, the gaps between them will increase. A new flame rod assembly will have about an ⅛ inch gap between the flame rods.

As the gap increases, it loses its ability to function properly and causes ignition failure. With time, the flame rods also get dirty. If they get too dirty, they won’t be able to produce a spark and the heater will go into ignition failure mode. That’s when the error code E003 pops up.

How To Fix:

More often than not, you’ll have to replace the flame rod assembly if there are issues with the flame rods. If they’re bent, then you’re better off replacing the flame rod assembly rather than trying to adjust their position.

However, if the flame rods are only dirty, you can fix the issue by cleaning them. You can use sandpaper or emery cloth to clean it. It can be hard to access the flame rod depending on your unit.

In my Navien tankless water heater, I’ll have to remove the blower to access the flame rods. I am using a Navien NR 240A water heater. The location of the flame rods can be different depending on your model.

I’ll explain how you can replace the flame rod assembly in a moment. If you want to know how you can clean them, follow that section. The only difference is that you’ll clean the flame rods when you have access to them instead of replacing them.

The issue can also be with any of the wires. If they’re loose, pinched, broken, or compromised in any way, you’d have to replace them. But the most likely scenario here is that you’ll have to replace the flame rod assembly. So, let’s look at how you can do it.

How To Clean And Replace Flame Rod Assembly Or Igniter In Navien Tankless Water Heater?

Replacing the flame rod can be tricky if you have no experience working on heaters. But don’t worry, I’ve done it many times and I’ve broken down the steps into a simple process.

Even if you have a faulty igniter, you’d have to replace the flame rod assembly as you won’t find it as an isolated unit. You can follow these steps to replace the flame rod assembly in your Navien water heater:

Step 01 – Remove The Blower

Turn off the power supply to the heater by pressing the power button on the heater. Then, remove its connection to the power outlet. Shut off the gas supply as well by turning off the gas valve. You can also wait for it to cool down if it was in use recently.

The main thing you’ll have to do to have access to the flame rod is remove the blower. Inspect the area around the blower. You’ll notice that you’ll have to take off three screws to remove the blower.

If you have a long screwdriver or an extension of a power tool, you’ll have a much easier time accessing these screws. Then, remove those screws. Keep in mind that all these screws are of different sizes.

When you take them out, arrange them in a way that you can put them back in the right order later on. If you do that, you’ll be saving yourself from a lot of frustration down the line.

Once you remove the screws, you can twist the blower and it’ll come out. You’ll have access to the flame rods as soon as you do that.

Step 02 – Pull Out The Old Flame Rod Assembly

You’ll notice two black insulation boots right where the flame rod is located. Here’s a picture to help you out and give you an idea of what the area you should be looking for:

flame rod assembly of navien tankless water heater

Once you disconnect those black insulation boots, you’ll notice two screws holding the flame rod assembly in place. You’ll have to remove them to remove the flame rod assembly. You can pull the flame rod assembly after you remove the screws.

Step 03 – Clean Or Replace The Flame Rod Assembly

If you have dirty flame rods, you can just clean them and put the heater back together. But I’d recommend replacing the flame rod assembly if you want a more long-term solution.

Now, you’ll have to put the new flame rod assembly in place of the old one. Make sure you seat the insulation properly so that the flame rod assembly doesn’t get damaged.

Plug the black insulation boots back in. Double-check that the flame rod wire isn’t under any pressure due to the new installation. It should be free and not pinched in.

Then, it’s time to mount the blower back to the heater. Place it in its position and reconnect the three screws you removed when you pulled it out. None of the wires should be pinched as you put everything back together. Then, place the outer cover of the heater back together to complete the job.

So, that’s how easy it is to do Navien flame rod replacement on your own. Although it’s a lengthy job, it’s not a complicated one. After completing the replacement, you can turn on the power supply and the gas supply.

Check if the issue gets solved after replacing the flame rod assembly. If it still persists, there’s another culprit behind this issue. Keep on reading to find out what it could be and how you can solve it.

05. Gas Pressure Issues

Merely having a functional gas supply isn’t enough for your Navien tankless water heater to run properly. The gas needs to be supplied at the right pressure if you want the unit to operate smoothly.

If the gas isn’t supplied at the right pressure, it can create several issues. One of those potential issues is ignition failure that’ll make the Navien code E003 come up.

You have to check your owner’s manual to know the right gas pressure for your unit. However, the gas pressure would normally have to be in the range of 5” WC to 10.5” WC for natural gas tankless heaters.

For LP gas tankless heaters, a good range is between 8” WC and 13.5” WC. However, keep in mind that these are estimates. Ideally, you should always follow the manufacturer’s guidelines for your unit.

So, the gas pressure needs to be at the right level. The first thing here is to look at the static gas pressure of the heater. If that’s okay, then you need to look at the gas pressure regulator next.

The gas regulator controls the flow of gas depending on the pressure. So, it needs to keep up with the flow rate. If it fails to do that, the heater won’t get enough gas. That will lead to ignition failure and cause the E003 code.

How To Fix:

You’ll have to measure the gas pressure to know if there’s any issue with it. There’s a device called a manometer that measures gas pressure. It has to be connected to the inlet port of the water heater to measure the pressure.

inlet port of navien tankless water heater

There’s a high chance that you won’t have a device like that lying around. So, get the help of a technician for this one. There are many things to check here. The static pressure as well as the pressure when the unit is heated.

If the static pressure is good but the pressure isn’t regulated properly, your heater will still work. But you’d have very little hot water if multiple faucets are used at the same time. So, get someone who knows about these things to solve this issue for you.

On top of that, there’s always the possibility that the fault could be with the gas pressure regulator. As it’s a relatively sensitive component that deals with gas, you shouldn’t mess around with it.

If you have a bad gas gas pressure regulator, it’ll have to be replaced. But don’t worry about doing it yourself. Consult a qualified technician approved by Navien for this job. If you do that, the replacement will go smoothly. Hopefully, that’ll get the error code to go away.

06. Bad Transformer

The transformer needs to be working in proper condition so that the heater can work well. If you have a bad transformer, it won’t send enough power to the igniter. So, the unit will not be ignited and you’ll see the E003 code.

transformer of navien tankless water heater

How To Fix:

If you have a bad transformer that keeps cutting on and off, you’ll have to replace it with a new one. Replacing the transformer is an easy job. The main challenge will be to locate it. Here’s a picture of the transformer in a Navein tankless water heater:

Based on your model, the location of the transformer can vary. But once you find it, all you’ll have to do is to remove the two screws holding it in place. Then, put the new transformer in place and tighten the screws again. Hopefully, that’ll solve the issue for you.

07. PCB Issues

The PCB needs to have the right settings. If it’s not set up properly according to the altitude, you’ll also get the E003 error code. However, if you have the right settings, there’s a bigger issue at play here.

Last but not least, a faulty PCB or motherboard can also cause ignition failure. It’s the worst possible culprit that could be responsible for this issue. If you’ve tried all the other fixes and none of them worked, there’s a strong chance that you have a bad PCB.

PCB of navien tankless water heater

How To Fix:

First of all, make sure that the PCB settings are perfect according to your elevation. If you don’t know how to check these things, contact Navien support. They’ll send someone to fix the issue.

The fix to faulty settings is quite simple. A few alterations to the dip switch settings would fix this issue. However, if the settings were correct to begin with, you could have a faulty PCB.

Unfortunately, you can’t get around the issue of a damaged PCB. You’ll have to replace it if you want a permanent fix for the error code. It’s not the easiest job to replace your Navien heater’s PCB on your own. Especially, if you don’t have prior experience of doing it.

But I’ve broken down the entire process as simply as I can. Hopefully, you’ll understand everything. Give them a read and if they seem too complicated, delegate the job to a technician.

How To Replace Navien Tankless Water Heater PCB?

I’ve replaced the PCB in my Navien NR 240A water heater. The exact process and location of the PCB may vary a bit depending on your model. But overall, the process will be pretty much the same. Without further ado, here are the steps to replace the PCB in your Navien water heater:

Step 01 – Turn Off The Heater

Turn off the electrical power to the heater. Unplug the connection of the heater too as an added measure of safety. Turn off the gas supply to the heater as well and remove the outer cover.

Once you do that, take a picture of the heater in its current state. Especially, focus on the wiring connections so that you don’t make a mistake later on. It’ll help you to put it back together correctly after you replace the PCB.

Step 02 – Remove PCB Connections

Then, you’ll have to disassemble the PCB. In some combi boiler units, you’d have to remove the display module in front of the board before you can access the PCB. But in my case, you can directly get to the PCB.

Locate the screws holding the PCB in place. There will be three screws in total – one on top of the control board and the other two will be underneath the heater. Once you remove these screws, the motherboard will come loose.

Now, you’d have to remove the wiring connections to the PCB. Then, you can remove the two connections at the back of the PCB. Once you do that, the PCB will be separated from the rest of the heater. At that stage, you can pull it out.

Step 03 – Install The New PCB

Place the new motherboard in place of the old one. Secure its position by tightening the screws. Then, take a good look at the picture you clicked earlier and attach the wiring connections.

Keep in mind that the heater won’t work if you make any mistakes when putting the wiring connections back together. So, make sure you install them correctly. Once you do that, put the front cover of the heater back on.

That’s how you can replace the PCB. Restore the gas supply to the water heater and turn it back on. The unit should now run without any issues after you’ve replaced the PCB and the error code should also go away.

At this stage, you’ve looked at all the most likely solutions to get rid of the E003 error code. If the problem still persists, you’re dealing with a unique problem. So, you’re bound to ask for the help of a technician if you’re dealing with this one-of-a-kind issue.


Is there an igniter in the Navien tankless water heater?

Yes, the igniter is a part of the flame rod assembly. When the igniter goes bad and you need to replace it, you’ll have to replace the entire flame assembly.

Why do the flame rods in my Navien tankless water heater get dirty so quickly?

The main reason behind it is abnormal gas pressure. If you run too many gas-powered components at the same time, it can mess up the gas flow. In that case, the flame rods can become dirty earlier than you’d expect.

Can you use water for Navien flame rod cleaning?

Only using dry things to clean Navien flame rods is recommended. Things like sandpaper, a dry piece of clothing, and emery cloth are good. But you shouldn’t use water to get the dirt out of the flame rods.

What temperature should you set your Navien water heater at?

The right temperature settings for you depend on your own comfort level. But I recommend setting it to 120°F or lower to eliminate the risk of scalding.

What does the Navien tankless water heater flashing red light mean?

The red light with a wrench icon means that the heater has gone into a soft lockout mode. The most common reason behind it is when one or more of the PCB connections are loose. So, inspect it and tighten any loose connections.


What causes Navien tankless water heater ignition failure and E003 error code? You should know all about it by now after completing this guide. Hopefully, it’ll be a simple issue like a power failure or a dirty air intake filter. You’ll be able to fix them easily.

The worst-case scenario is a faulty PCB. But even if that happens, you know how to replace it. I think you’ll solve your problem if you follow this guide well. I also have a dedicated guide on fixing the Navien tankless E110 error code. Check it out if you’re interested.

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