Navien Tankless Hot Water Heater Error Codes: Your Complete Guide

There’s nothing quite like the jolt of a morning shower turning ice-cold. You head to your Navien tankless unit, only to be greeted by a blinking number on the digital display. It’s a frustrating moment we see all the time, but that little screen is actually your best friend in disguise.

I promise that by the end of this article, you’ll understand what those cryptic numbers mean. We’re going to translate the most common navien tankless hot water heater error codes from confusing jargon into plain English, giving you the confidence to solve the simple problems and the wisdom to know when to call for backup.

Together, we’ll walk through a complete navien tankless hot water heater error codes guide, covering what causes these faults, how to safely troubleshoot them, and the best practices to prevent them from ever coming back. Let’s get that hot water flowing again!

Why Your Navien Unit Is Smarter Than You Think: Understanding Error Codes

First things first, let’s reframe how we think about that error code. It’s not a sign of failure; it’s a form of communication. Your high-efficiency Navien unit is packed with sensors that constantly monitor its performance, from gas pressure and water flow to exhaust temperatures.

When one of these sensors detects an issue, it displays a code to pinpoint the exact problem. This is one of the key benefits of navien tankless hot water heater error codes—they take the guesswork out of diagnostics, saving you time and money on service calls.

Instead of a vague “it’s not working,” your unit is telling you, “Hey, my exhaust is a little too hot,” or “I’m having trouble sensing a flame.” This allows you, or your technician, to get right to the source of the issue.

The Most Common Navien Tankless Hot Water Heater Error Codes and What They Mean

Alright, let’s get to the heart of the matter. While Navien has dozens of potential codes, most of the issues we see in the field boil down to a handful of common culprits. We’ll break them down by category so you can easily find what you’re looking for.

Ignition and Flame Errors (Codes 001, 003, 010)

These codes relate to the very beginning of the heating process: creating and sustaining a flame. They are often linked to your gas supply or the internal components that manage combustion.

Error Code 001 (Ignition Failure): This means your unit tried to light the burner several times but couldn’t establish a stable flame. It’s trying, but something is stopping it.
- Common Causes: No gas supply, low gas pressure, a dirty flame sensor, or a blocked vent pipe.
- DIY Checks: First, check other gas appliances (like your stove) to confirm your home has gas. Ensure the small gas valve handle leading to the unit is parallel (in the “on” position) with the pipe. Safely check the exterior vent terminations for any obvious blockages like leaves or a bird’s nest.
Error Code 003 (Flame Loss): The unit successfully lit, but the flame went out while it was running.
- Common Causes: This is often caused by external factors like extremely high winds blowing down the vent pipe, a clogged condensate drain backing up water into the unit, or an issue with the gas pressure regulator.
- DIY Checks: Check your condensate drain line (the small plastic tube at the bottom) for any clogs or kinks. Ensure it’s draining freely. Also, check the exterior vents for obstructions.

Exhaust and Ventilation Errors (Codes 012, 016)

Your Navien needs to breathe. It pulls in fresh air for combustion and pushes out exhaust fumes. If that process is compromised, the unit will shut down for safety.

Error Code 012 (Abnormal Fan Speed): The internal fan that pushes exhaust out isn’t spinning at the correct speed—either too fast or too slow.
- Common Causes: A blockage in the intake or exhaust vent, strong winds affecting the fan, or a failing fan motor.
- DIY Checks: Your main job here is a visual inspection of the vent pipes outside. Is there a heavy snowdrift covering them? Did a plastic bag get sucked up against the intake? Clearing these can often resolve the code.
Error Code 016 (Air Pressure Sensor Issue): This is closely related to code 012. A sensor has detected an issue with the air pressure inside the unit, usually tied to a venting problem.
- Common Causes: Blocked vents are the number one cause. It can also be triggered by an incorrect vent installation (pipes are too long or have too many elbows) or a faulty sensor.
- DIY Checks: Again, a thorough visual check of your exterior vent terminations is the best first step.

Water Flow and Temperature Errors (Codes 002, 030, E787)

These codes point to problems with the water moving through the unit or the heat exchanger getting too hot, which are often related issues.

Error Code 030 (High Exhaust Temperature): This is a critical one. It means the temperature inside the heat exchanger has exceeded a safe limit. This is one of the most common problems with navien tankless hot water heater error codes and is almost always caused by one thing: scale buildup.
Error Code E787 (Flow Sensor Abnormality): The unit is having trouble detecting the correct rate of water flowing through it.
- Common Causes for Both: Mineral scale from hard water coating the inside of the heat exchanger is the primary villain. This buildup acts like insulation, forcing the unit to work harder and overheat. It also restricts water flow, which can trigger the flow sensor error. A clogged water inlet filter is another common cause.
- DIY Checks: Check and clean the aerators on your faucets and showerheads. If they are clogged with sediment, it’s a good sign the inside of your heater is too. You can also clean the small screen filter on the cold water inlet of the unit (consult your manual for its exact location).

How to Safely Troubleshoot Navien Tankless Hot Water Heater Error Codes

Okay, you’ve identified your code. Don’t panic. Before you pick up the phone, follow this simple, safe troubleshooting sequence. This is a great set of how to navien tankless hot water heater error codes tips that can solve many common issues.

Write Down the Code: Don’t just reset the unit right away. The code is valuable information. Write it down so you can reference it or tell your technician if needed.
Perform a Power Cycle (Reset): The oldest trick in the tech book often works. Unplug your Navien unit from the wall outlet, wait for a full five minutes, and then plug it back in. This allows the internal computer to fully reset. Never just rapidly turn it off and on.
Conduct a Safe Visual Inspection:
- Venting: Look at your exterior intake and exhaust pipes. Are they blocked by snow, ice, leaves, or animal nests? Clear any obstructions.
- Condensate Line: Find the clear or white plastic tube at the bottom of the unit. Is it kinked, clogged, or frozen? Ensure it has a clear path to drain.
- Valves: Check the three valves below your unit. The red (hot water), blue (cold water), and yellow (gas) valve handles should all be parallel to the pipes, indicating they are fully open.
Check Water Fixtures: Unscrew the aerator from your kitchen or bathroom faucet. Is the screen filled with white, chalky debris? Clean it out and see if hot water flow improves. This is a strong indicator that you need to descale your unit.

Preventative Maintenance: Your Best Defense Against Error Codes

The absolute best way to deal with error codes is to never see them in the first place. Following a simple navien tankless hot water heater error codes care guide will dramatically extend the life of your unit and improve its efficiency. Adhering to these best practices is also a more sustainable and eco-friendly approach to homeownership, as an efficient unit uses less energy.

Annual Descaling is Non-Negotiable

If you live in an area with hard water (and most of us do), mineral scale is silently building up inside your heater’s delicate heat exchanger. This forces the unit to work harder, leads to overheating error codes like 030, and will eventually cause a catastrophic failure.

We recommend a professional descaling service once a year. This process involves circulating a special solution (like food-grade vinegar) through the unit to dissolve all the mineral buildup, restoring it to factory performance.

Keep Your Vents and Filters Clean

Make it a seasonal habit to check your exterior vents. A quick glance in the spring and fall can prevent a no-hot-water emergency in the winter. At the same time, clean the cold water inlet filter screen to ensure strong, steady flow into the unit.

When to Put Down the Tools and Call a Certified Navien Technician

While we encourage homeowners to be proactive, safety is always priority number one. You should immediately call a licensed and certified professional if you encounter any of the following situations:

You smell gas: If you smell gas near the unit, do not touch anything electrical. Leave the home immediately and call your gas utility’s emergency line from a safe distance.
The error code returns after a reset: If you’ve power-cycled the unit and checked the basics, but the code keeps coming back, it’s a sign of a deeper issue with a component that needs professional diagnosis.
You see water leaking FROM the unit: A drip from a fitting is one thing, but if water is coming from the casing itself, turn off the water to the unit and call for service right away.
You are uncomfortable with any step: If you’re not 100% confident, it’s always better to call a pro. That’s what we’re here for!

Frequently Asked Questions About Navien Tankless Hot Water Heater Error Codes

How do I reset my Navien tankless water heater?

The simplest way is to press and hold the power button on the front panel until it turns off, wait about a minute, and then press it again to turn it back on. For a “hard reset,” unplug the unit from its power outlet for five minutes before plugging it back in.

Why does my Navien keep showing an error code in cold weather?

This is very common. The two most likely culprits are a frozen condensate line, which blocks drainage and shuts the unit down, or high winds causing pressure issues in the venting system. Ensure your condensate line is insulated if it runs through an unheated space.

Can I fix all Navien error codes myself?

No. While you can resolve many common codes related to blockages or flow issues, any code pointing to an internal component failure—like a gas valve, fan motor, or main control board—requires a certified technician with specialized tools and training to diagnose and repair safely.

That blinking code on your Navien unit doesn’t have to be a mystery. By understanding what it’s trying to tell you and following these simple, safe steps, you can often get your hot water back on in minutes.

Remember, the foundation of a reliable system is consistent maintenance. Think of descaling and cleaning as an investment in your home’s comfort and your unit’s longevity. You’ve got this!

Stay safe, stay comfortable, and enjoy that endless hot water!

Author
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David Clark

Founder & Lead HVAC Specialist at HVACRLY

David Clark is the founder of HVACrly and a certified HVAC specialist with 10+ years working on residential and light-commercial systems. He turns complex heating, cooling, ventilation, and refrigeration topics into clear, actionable guides focused on safety and energy efficiency. When he’s not on a service call, he’s testing tools and writing step-by-step tutorials.