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What Your Navien Error Code Means and How to Fix It

By Peter Gray
Updated
Stuck on a blinking code? Match it, then get the shower hot again.

A blinking error code on your Navien tankless water heater is the unit telling you exactly what went wrong, from a failed ignition to a clogged filter or an overheating heat exchanger.

The catch is that the code only helps if you know what it means. A quick filter clean fixes some of them at home; others point to a part that needs a technician.

Below is the full list of Navien error codes, what each one is reporting, and the fix to try first so you can get the hot water back.

Key Takeaways

  • Each Navien error code names a specific fault, such as an ignition failure, flame loss, or a sensor problem.
  • Filter-related codes like E012, E016, and E110 often clear once you clean the air intake or cold water inlet filter.
  • Hard water scale is the top cause of overheating and heat exchanger faults, so descale the unit once a year.
  • For a code that returns after a reset, call Navien support at 1-800-519-8794 (5 AM to 6 PM Pacific, Monday through Friday).

In This Article

Navien Tankless Error Codes Breakdown

Tankless water heater systems rely on a synchronized dance of sensors, fans, and valves. When one steps out of line, the system halts to protect itself. Below is a comprehensive list of error codes to speed up your troubleshooting process.

Error Code E003

What It Is Telling You

  • Ignition failure: The unit tried to light the burner but failed.

The Solution

  1. Check the gas: Ensure your main gas valve is fully open.
  2. Check the supply: If other gas appliances in the house aren’t working, you may have a utility outage.

Error Code E004

What It Is Telling You

  • False flame detection: The sensor thinks there is a flame when there shouldn’t be one.

The Solution

  1. Check grounding: Verify the main electrical cord is properly grounded to the outlet.
  2. Inspect the sensor: The flame rod may be dirty or touching the burner.

Error Code E012

What It Is Telling You

  • Flame loss: The fire lit successfully but went out unexpectedly.

The Solution

  1. Clean the air intake filter: Turn off the power, remove the filter, and scrub it with a toothbrush under running water. Dry it completely before reinstalling.
  2. Check the connections: Ensure the electrical cord is grounded and there are no loose wires inside the panel.

Error Code E016

What It Is Telling You

  • Overheating: The heat exchanger has exceeded safe temperatures.

The Solution

  1. Restart the unit: Turn the system off for 30 minutes to let it cool down, then restart it.
  2. Clean the cold water inlet filter: Remove the filter and rinse away any debris.
  3. Flush the unit: Scale buildup often causes overheating. Flush the heat exchanger with white vinegar or a descaling solution, circulating it for 45 to 60 minutes and then rinsing with fresh water for at least 10 minutes (1).

Error Code E030

What It Is Telling You

  • Exhaust overheating: The flue gas temperature has spiked above 149 degrees Fahrenheit.

The Solution

  1. Cool down and reset: Turn the unit off for at least 30 minutes.
  2. Clean the inlet filter: Remove the water inlet filter and scrub it clean.
  3. Check for scale: If this happens often, your heat exchanger is likely clogged with mineral deposits and needs flushing.

Error Code E046

What It Is Telling You

  • Limit control issue: The heat exchanger limit switch is open.

The Solution

  1. Contact support: Call Navien technical support at 1-800-519-8794.

Error Code E047

What It Is Telling You

  • Exhaust thermostat issue: There is a problem with the exhaust sensor or grounding.

The Solution

  1. Contact support: Call Navien technical support at 1-800-519-8794.

Error Code E060

What It Is Telling You

  • Dual venturi issue: The mechanism that controls the air/gas mix is malfunctioning.

The Solution

  1. Contact support: Call Navien technical support at 1-800-519-8794.

Error Code E109

What It Is Telling You

  • Fan motor issue: The fan isn’t spinning correctly.

The Solution

  1. Clean the air filter: A dirty air intake filter puts stress on the fan. Wash it, dry it, and reinstall it.

Error Code E110

What It Is Telling You

  • Abnormal air pressure: The system isn’t getting enough air or can’t push exhaust out.

The Solution

  1. Check for blockages: Look at your exhaust venting outside. Ensure no birds’ nests, snow, or leaves are blocking the pipe.
  2. Clean the filter: Wash the air intake filter thoroughly.

Error Code E407

What It Is Telling You

  • Hot water outlet issue: The thermistor (temperature sensor) is open or shorted.

The Solution

  1. Contact support: Call Navien technical support at 1-800-519-8794.

Error Code E421

What It Is Telling You

  • Cold water inlet 1 issue: The thermistor is open or shorted.

The Solution

  1. Contact support: Call Navien technical support at 1-800-519-8794.

Error Code E432

What It Is Telling You

  • Cold water inlet 2 issue: The thermistor is open or shorted.

The Solution

  1. Contact support: Call Navien technical support at 1-800-519-8794.

Error Code E434

What It Is Telling You

  • Water adjustment valve issue: The valve is operating abnormally.

The Solution

  1. Contact support: Call Navien technical support at 1-800-519-8794.

Error Code E438

What It Is Telling You

  • Circulation pump issue: The pump is struggling or failing.

The Solution

  1. Check the lines: Ensure all water return and supply lines are open and not kinked.
  2. Internal check: Verify the direction of the two-way valve if you are comfortable working inside the unit.

Error Code E439

What It Is Telling You

  • Flow sensor issue: The sensor isn’t reading water flow correctly.

The Solution

  1. Contact support: Call Navien technical support at 1-800-519-8794.

Error Code E441

What It Is Telling You

  • Hot water inlet 2 issue: The thermistor is open or shorted.

The Solution

  1. Contact support: Call Navien technical support at 1-800-519-8794.

Error Code E445

What It Is Telling You

  • Bypass mixing valve issue: The valve is operating abnormally.

The Solution

  1. Contact support: Call Navien technical support at 1-800-519-8794.

Error Code E515

What It Is Telling You

  • PCB issue: The main control board is behaving abnormally.

The Solution

  1. Check power: Ensure the main electrical cord is grounded. Reset the unit.

Error Code E517

What It Is Telling You

  • DIP switch setting: The configuration switches on the board are incorrect.

The Solution

  1. Contact support: Call Navien technical support at 1-800-519-8794.

Error Code E593

What It Is Telling You

  • Front panel key issue: A button on the display may be stuck.

The Solution

  1. Contact support: Call Navien technical support at 1-800-519-8794.

Error Code E615

What It Is Telling You

  • Memory issue: The input information in the computer is corrupted.

The Solution

  1. Contact support: Call Navien technical support at 1-800-519-8794.

Error Code E736

What It Is Telling You

  • Cascading communication issue: Problem communicating between multiple linked units.

The Solution

  1. Contact support: Call Navien technical support at 1-800-519-8794.

Error Code E740

What It Is Telling You

  • Outdoor sensor issue: The external temperature sensor is malfunctioning.

The Solution

  1. Contact support: Call Navien technical support at 1-800-519-8794.

Error Code E760

What It Is Telling You

  • Maintenance alarm: The unit is reminding you to flush or service the system.

The Solution

  1. Service required: Perform a system flush or contact a professional for annual maintenance.

Error Code E782

What It Is Telling You

  • Main panel communication issue: The display isn’t talking to the main board.

The Solution

  1. Contact support: Call Navien technical support at 1-800-519-8794.

Error Code E785

What It Is Telling You

  • Flow switch issue: The sensor detects flow when there is none, or vice versa.

The Solution

  1. Contact support: Call Navien technical support at 1-800-519-8794.

Common Navien Tankless Water Heater Problems

Navien’s tankless water heaters are top-tier competitors in the market, but like any appliance, they have their quirks. While older models (specifically pre-2011) had a rocky reputation with recalls, the newer NPE series has ironed out most of those bugs.

However, even the best units run into trouble eventually. Here are the most common hardware issues owners face.

Turn The Power Off

Before doing anything else with your unit, make sure the power is off. Although it is a gas-powered boiler, it still uses electricity. To stay safe while working on your boiler, switch the breaker to the “Off” position.

1. Motherboard and Control Board Failure

The motherboard is the brain of your heater. If it fails, the whole system goes dark. This was a frequent plague on older models, but it can still happen today due to power surges or moisture damage.

Symptoms include the unit turning on and off randomly or the display going completely blank. If you see Error Code E003 (ignition failure) but your gas supply is fine, the control board might be sending ghost signals.

The Fix: Try a hard reset by unplugging the unit for 30 minutes. If the behavior continues, you likely need a new board installed by a pro.

2. Flow Sensor Corrosion

The flow sensor tells the unit to fire up when you open a tap. If this sensor gets dirty or corroded, the heater won’t know you need hot water, and it will stay cold.

Older units used materials prone to rust, but even modern stainless steel sensors can get coated in mineral buildup if you have hard water.

The Fix: Turn off the unit and water supply. Remove the flow sensor, clean it gently, and blow on the turbine to ensure it spins freely. If it is heavily corroded, you will need to buy a replacement part.

3. Heat Exchanger Cracking

This is the worst-case scenario. The heat exchanger is the heart of the machine. If it cracks, you might smell exhaust fumes or notice water leaking from the bottom of the casing. This is dangerous because it can allow carbon monoxide to escape into your home.

The Fix: Shut the unit down immediately. There is no DIY fix for a cracked exchanger, so it has to be replaced. The upside is that Navien’s residential NPE warranty covers the heat exchanger for 10 years, with 5 years on other parts and 1 year on labor, so check your registration date before you pay for a new unit (2).

How to Reset a Navien Tankless Water Heater

If your water is cold but you don’t see a specific error code, a system reset is your best first move. It acts like rebooting a computer, clearing out temporary glitches.

Navien makes this simple:

  1. Locate the front control panel.
  2. Find the Reset button (usually near the Power button).
  3. Press it once.
  4. Wait for the system to cycle back on.

If the unit resets but the error comes back immediately, you have a hard part failure that needs attention.

Where Is the Serial Number on a Navien Water Heater?

When you call technical support, the first thing they will ask for is your serial number. Having this ready saves you a headache.

You can usually find the serial number on a data sticker located on the right side of the unit. It typically includes the model number, energy guide info, and a barcode.

If you don’t see it on the side, check the inside of the front cover door.

FAQs

How Do You Troubleshoot a Navien Water Heater?

To troubleshoot a Navien water heater, start with the error code on the front display and match it to the list above to pin down the failure, whether it is ignition, airflow, or a sensor. If no code shows, confirm the gas and water valves are fully open, clean the air intake filter, and press the reset button on the panel. A code that comes back right after a reset points to a hardware fault that needs a technician.

Where Is the Reset Button on a Navien Tankless Water Heater?

The reset button sits on the front control panel, usually as a separate button labeled “Reset” next to the “Power” button. You do not need to open the front cover or touch any internal wiring. Press it once and wait for the unit to cycle back on.

How Long Do Navien Tankless Water Heaters Last?

A Navien tankless water heater can last up to 20 years, well beyond the 10 to 12 years typical of a conventional tank heater. That lifespan depends on yearly maintenance, though. Skip the annual descaling and mineral scale will shorten the heat exchanger’s life.

Is Navien a Good Brand of Water Heaters?

Yes, Navien is one of the better-known names in the tankless market, recognized for high-efficiency condensing technology and long warranty coverage. Early models drew reliability complaints, but the current NPE-A and NPE-S series are popular with plumbers for their easier installation and steadier performance.

How Long Is Navien Warranty?

For residential NPE units, Navien’s warranty covers the heat exchanger for 10 years, other parts for 5 years, and labor for 1 year, measured from the original installation date. Terms change for commercial or heating use and can vary by model, so check your own paperwork and register the unit after installation.

What Maintenance Is Required for a Navien Tankless Water Heater?

Descale the unit once a year with white vinegar or a descaling solution to clear mineral scale, circulating it for 45 to 60 minutes and then rinsing with fresh water for about 10 minutes. Very hard water can call for descaling roughly every six months. Clean the air intake filter and cold water inlet filter yearly too, scrubbing them with a toothbrush under cold running water and drying them fully before reinstalling.

What Is the Difference Between Navien NPE-a and NPE-S?

The main difference is the recirculation pump. The NPE-A (“Advanced”) series has a built-in buffer tank and recirculation pump for near-instant hot water at the tap. The NPE-S (“Standard”) series drops that pump, so it costs less but takes a few seconds longer to deliver hot water. Choose the A model if you dislike waiting at the faucet, the S model if budget matters most.

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About the Author

Peter Gray

Peter writes step-by-step guides that help homeowners fix leaks, replace faucets, and handle common plumbing repairs without calling someone in. Because he worked in the trade, he can also tell you which jobs are straightforward to do yourself and which ones are worth leaving to a licensed plumber.

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Categories Water Heating