Navien Water Heater Stopped Working - 7 Common Causes & How To Fix

There’s nothing quite like the shock of a cold shower when you’re expecting a steamy, relaxing one. You stand there, shivering, wondering what went wrong. If you have a Navien tankless water heater, that sudden lack of hot water can feel especially frustrating. These units are marvels of efficiency, but like any sophisticated machine, they can run into issues.

I hear it all the time from homeowners: “My navien water heater stopped working, and I don’t know where to start.” It’s a common and stressful situation.

But here’s the good news. As an HVACR technician, I can promise you that many of the most common problems are things you can safely diagnose and even fix yourself with a little guidance. We’re going to solve this problem together.

In this complete navien water heater stopped working guide, we’ll walk through the exact same steps a pro would take, from the simplest checks to more advanced troubleshooting. We’ll decode error codes, clean essential filters, and pinpoint exactly when it’s time to call for backup. Let’s get that hot water flowing again.

First Things First: The Simple Checks Before You Panic

Before you start taking things apart, let’s cover the basics. You’d be surprised how often the solution is simple. When a customer calls me saying their Navien water heater stopped working, these are the very first questions I ask.

1. Check Your Power Supply

Your Navien tankless heater needs electricity to operate its control board, igniter, and fan. It’s an easy thing to overlook.

Find Your Breaker Box: Head to your home’s electrical panel. Look for the breaker labeled “Water Heater,” “Tankless,” or “Navien.”
Reset the Breaker: Flip the breaker firmly to the “OFF” position, then back to the “ON” position. Sometimes breakers can “trip” without looking like they’ve moved.
Check the Outlet: Most Navien units plug into a standard wall outlet. Ensure it’s plugged in securely. If it’s a GFCI outlet (with “Test” and “Reset” buttons), press the “Reset” button.

2. Verify Your Gas or Propane Supply

No fuel means no flame, and no flame means no hot water. It’s a simple equation.

For Natural Gas: Check the gas valve on the line leading to your water heater. The handle should be parallel to the pipe, indicating it’s open. If it’s perpendicular, it’s closed. Also, check if other gas appliances in your home (like a stove) are working. If not, you may have a larger gas supply issue.
For Propane (LP): Go outside and check the gauge on your propane tank. It’s possible you’ve simply run out of fuel.

3. Is the Unit Itself Turned On?

This might sound obvious, but it happens! Someone might have accidentally turned it off. Check the power button on the front control panel of your Navien unit. If the screen is blank, press the power button to see if it comes to life.

Decoding the Brains: Understanding Navien Error Codes

One of the best features of a Navien heater is its self-diagnostic system. When it detects a problem, it will usually display an error code on the front panel. This code is your biggest clue.

Don’t be intimidated by these codes. Think of them as your heater’s way of telling you exactly what’s wrong. This is one of the most useful navien water heater stopped working tips I can give you: always check for an error code first.

Common Navien Error Codes and What They Mean

While your user manual has a full list, here are a few of the most common culprits:

Error Code E003 (or 003E): This almost always points to an ignition failure. The unit tried to light the burner three times and failed. This could be a gas supply issue (like we checked above), a blocked vent, or a problem with the igniter or flame sensor.
Error Code E012 (or 012E): This indicates a flame loss. The heater started successfully but the flame went out unexpectedly. This often points to irregular gas pressure or an issue with the exhaust or condensate drain.
Error Code E110 (or 110E): This signals a problem with the air pressure sensor or venting. The unit isn’t “breathing” correctly. The first step here is to check your vent pipes outside for blockages.

How to Reset Your Navien Water Heater

Sometimes, a temporary glitch can cause an error. A simple reset can clear it. To do this, simply unplug the unit from the wall outlet, wait for a full 60 seconds to allow the internal capacitors to discharge, and then plug it back in. This is different from just turning it off and on at the panel.

Pro Tip: If the same error code comes back immediately after a reset, it means there’s a real, persistent problem that needs to be addressed. The reset is a diagnostic step, not a permanent fix.

The #1 Culprit: When Your Navien Water Heater Stopped Working Due to Flow Issues

Here’s a core concept for tankless heaters: they only turn on when they detect a sufficient flow of water. If the water flow is too weak, the unit will remain off to protect itself. Many of the common problems with Navien water heater stopped working are related to this.

Step-by-Step: Cleaning the Inlet Water Filter Screen

Your Navien has a small filter on the cold water inlet pipe to catch sediment and debris. If this clogs, it will restrict flow and prevent the heater from firing up.

Turn Off the Water: Locate the three valves on the pipes connected to the bottom of your Navien. Turn the handle on the cold water inlet (usually blue) and the hot water outlet (usually red) to the perpendicular (closed) position.
Relieve the Pressure: Open the small pressure relief valve levers on the service valves. A little water will drain out—this is normal. Have a small bucket ready.
Locate and Remove the Filter: The cold water inlet connection has a small, round filter screen right inside. You may need a flathead screwdriver or needle-nose pliers to gently pry it out.
Clean the Filter: Rinse the filter screen thoroughly under a sink. Use an old toothbrush to gently scrub away any stubborn mineral buildup or debris.
Reinstall and Test: Carefully place the clean filter back in, close the pressure relief levers, and slowly open the water valves again. Turn on a hot water tap and see if your heater fires up.

Check Your Faucet Aerators and Shower Heads

If the hot water isn’t working at just one or two faucets, the problem might not be the heater at all! The small screens (aerators) on the tips of your faucets and in your shower heads can get clogged with sediment, reducing flow below the Navien’s activation threshold. Unscrew them and clean them out.

Airflow and Exhaust: The Lungs of Your Tankless Heater

For your Navien to burn fuel safely and efficiently, it needs a clear path for fresh air to come in and exhaust fumes to go out. A blockage in this system will cause the heater to shut down as a safety measure.

Inspect Intake and Exhaust Vents for Blockages

Go outside to where your heater’s PVC pipes terminate. Look for any obstructions. Common culprits include:

Leaves, twigs, and debris
Bird or rodent nests
Heavy snow or ice buildup in the winter
Insect hives or webs

Clear away anything that might be blocking the openings. This simple step is a key part of any navien water heater stopped working best practices checklist.

Understanding the Condensate Drain

High-efficiency condensing heaters like Navien produce acidic water (condensate) as a byproduct. This water must drain away properly through a small tube. If this drain line becomes clogged or frozen, water will back up into the unit, and a safety switch will shut the heater down. Ensure the condensate line is clear and has a proper downward slope.

The Importance of Regular Maintenance: A Proactive Care Guide

The absolute best way to deal with a “navien water heater stopped working” situation is to prevent it from ever happening. Regular maintenance is not just a suggestion; it’s essential for the health and efficiency of your unit. This is the cornerstone of any good navien water heater stopped working care guide.

Following a maintenance schedule also promotes a more sustainable navien water heater stopped working solution, as a well-maintained unit uses less energy and lasts longer, which is an eco-friendly navien water heater stopped working approach.

Annual Descaling: The Key to Longevity

If you live in an area with hard water, minerals like calcium and magnesium will build up inside the heater’s delicate heat exchanger over time. This scale acts like an insulator, forcing the unit to work harder and eventually restricting water flow, causing it to shut down.

Descaling (or flushing) the unit annually with a vinegar solution or a dedicated descaling product removes this buildup, restores efficiency, and dramatically extends the life of your heater.

When to Put Down the Tools and Call a Certified Pro

While we’ve covered many DIY-friendly fixes, there are times when you absolutely need to call a licensed and certified Navien technician. Your safety is the top priority.

Call a professional immediately if you experience any of the following:

You smell gas: Do not touch any electronics. Leave the area immediately and call your gas company from a safe distance, then call an HVAC pro.
Visible water leaks from the unit’s casing: This could indicate a serious internal failure.
Error codes that persist after you’ve checked all the basic causes (vents, filters, gas, power).
Loud or unusual noises like banging, grinding, or screeching.
If the troubleshooting involves opening the main cover to access internal components like the gas valve, circuit board, or burner assembly.

Frequently Asked Questions About a Navien Water Heater That Stopped Working

Why is my Navien water heater clicking but not turning on?

That clicking sound is the igniter trying to light the gas. If it clicks several times and then stops (often followed by an E003 error code), it means the ignition failed. This usually points to a lack of gas, a blocked vent preventing proper airflow, or a dirty flame sensor that needs to be professionally cleaned.

How often should I service my Navien tankless water heater?

It is highly recommended to have your Navien unit professionally serviced once a year. This service should include a safety inspection and, most importantly, a descaling/flush of the heat exchanger, especially if you have hard water. This preventative maintenance is the best way to avoid unexpected breakdowns.

Can a simple power outage cause my Navien to stop working?

Yes. After a power outage, your Navien should restart automatically. However, a power surge during the outage can sometimes trip the internal safety features or the circuit breaker. If it doesn’t come back on by itself, try the full reset procedure (unplug for 60 seconds, then plug back in) and check your breaker panel.

Tackling a problem with your Navien water heater can feel daunting, but by following these steps, you’re empowered to solve the most common issues yourself. You’ve learned how to check the essentials, decode its messages, and clear the pathways for water and air to flow freely.

Remember to always prioritize safety. If you ever feel unsure or the problem seems beyond these basic checks, don’t hesitate to call a qualified technician. They have the specialized tools and training to get your hot water running safely and reliably.

Stay warm and stay comfortable!

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.