Navien Water Heater Won'T Turn On - Your 7-Step Technician-Approved

There’s nothing quite like the jolt of an unexpectedly cold shower to ruin your morning. You turn the handle, wait for that familiar rush of warmth, but all you get is icy water. When your high-efficiency Navien water heater won’t turn on, it can feel like a major household crisis.

But before you start imagining expensive repair bills, take a deep breath. As an HVACR technician, I can tell you that many of the reasons a Navien unit fails to fire up are surprisingly simple and often something you can safely diagnose yourself. This isn’t just about fixing a problem; it’s about understanding how your system works to prevent future issues.

I promise this guide will walk you through the exact same steps a professional would take when first arriving at your home. We’ll start with the absolute basics, decode those cryptic error codes, and give you a clear roadmap to follow. You’ll learn how to identify the issue, what you can safely handle, and precisely when it’s time to call for backup.

Let’s get that hot water—and your peace of mind—flowing again.

First Things First: The Simple Checks Before You Panic

Before we dive into the internal workings of your Navien, let’s cover the basics. You’d be amazed how often the solution is found here. Think of this as the essential pre-flight check for your water heater.

Is It Getting Power?

It sounds obvious, but it’s the number one culprit. Navien tankless heaters need electricity to operate their controls, fan, and igniter.

Check the Circuit Breaker: Head to your home’s electrical panel. Look for the breaker labeled “Water Heater” or similar. If it’s tripped (in the middle or off position), flip it firmly to the “OFF” position and then back to “ON”.
Verify the Outlet: Many Navien units plug into a standard outlet. Ensure the plug is seated firmly. To be certain the outlet itself has power, unplug the water heater and test the outlet with a small lamp or a phone charger you know works.
Look for a Power Switch: Some installations include a power switch near the unit that looks like a light switch. Make sure it hasn’t been accidentally turned off.

Is the Gas or Propane Flowing?

No fuel means no flame. This is another fundamental check that can save you a lot of headaches.

Find the Gas Valve: Locate the gas line running to your Navien unit. There will be a small valve with a handle. The handle should be parallel to the gas pipe, indicating it’s open. If it’s perpendicular, it’s closed—gently turn it to the open position.
Check Other Gas Appliances: Do your gas stove or furnace work? If other gas appliances are also out, the problem might be with your gas supply itself. Contact your utility company immediately.
For Propane Users: If your system runs on propane, go outside and check the gauge on your tank. You might simply be out of fuel.

What Does the Remote Controller Say?

The wall-mounted remote controller is your command center. An incorrect setting can prevent the unit from firing.

Ensure the unit is turned on and the temperature is set high enough to call for heat (typically above 100°F). If the screen is blank, it could be another sign of a power issue or a problem with the controller wire itself.

Decoding Your Navien: Understanding Common Error Codes

One of the best features of a Navien water heater is its ability to self-diagnose. When something is wrong, it will usually display an error code on the front panel or remote. This code is your most valuable clue. This section is your go-to for understanding the common problems with navien water heater won’t turn on scenarios.

Code E001 / E012 – Ignition Failure

This means the unit tried to light the burner but failed. It’s trying to create a flame but can’t confirm one is present.

Potential Causes: No gas supply (see above!), a dirty or faulty flame sensor, a bad igniter, or incorrect gas pressure.
What You Can Do: Double-check your gas supply is on. You can try resetting the unit by unplugging it for 30 seconds and plugging it back in. If the error persists, the issue is likely with an internal component like the igniter or flame sensor, which requires a professional.

Code E110 – Abnormal Water Flow or No Water

This is one of the most frequent issues. The unit isn’t detecting enough water flowing through it to safely turn on the burner. Safety first! The heater won’t fire if it can’t be sure the heat will be carried away by water.

Potential Causes: A clogged inlet water filter, very low household water pressure, or a faulty flow sensor.
What You Can Do: Cleaning the inlet water filter is a fantastic DIY step we’ll cover in detail next.

Code E003 / E010 – Abnormal Exhaust or Blocked Vent

Your Navien needs to breathe. This code means there’s a problem with the intake (fresh air) or the exhaust (combustion gases).

Potential Causes: A bird’s nest, leaves, snow, or ice blocking the exterior vent pipes. It could also indicate a problem with the internal fan or pressure switch.
What You Can Do: Safely inspect the outdoor vent terminations. Clear away any visible debris. If the vents are clear and the error continues, it’s time to call a pro, as the issue is internal. Do not operate a unit with a persistent exhaust error, as it can be a carbon monoxide risk.

Your In-Depth Navien Water Heater Won’t Turn On Troubleshooting Guide

If the basic checks didn’t solve it, let’s roll up our sleeves. This step-by-step navien water heater won’t turn on guide will walk you through the most common DIY-friendly fixes. Before starting, turn off the power to the unit at the breaker for safety.

Step 1: Clean the Inlet Water Filter

A clogged inlet filter is the prime suspect for flow-related issues (like error E110). It’s a small mesh screen on the cold water inlet designed to catch sediment before it enters the heater.

Shut Off the Water: Locate the service valves on the pipes below your unit. Turn the handle on the blue (cold) valve so it’s perpendicular to the pipe.
Relieve the Pressure: Open a hot water tap somewhere in your house to relieve any pressure in the line.
Locate and Remove the Filter: On the bottom of the cold water inlet connection, you’ll see a small plug or cap. Place a small bucket underneath to catch water. Unscrew this cap—you may need pliers. The small mesh filter should come out with it.
Clean the Filter: Gently rinse the filter under a faucet, using an old toothbrush to scrub away any sediment or scale. It should be completely clean.
Reassemble: Carefully reinsert the filter and screw the cap back on, ensuring it’s snug but not overtightened. Turn the water back on slowly and check for leaks before restoring power.

Step 2: Inspect the Condensate Drain

High-efficiency condensing units like Navien produce acidic condensation that must drain away. If this drain line gets clogged, a safety switch will shut the unit down to prevent water damage.

Follow the small plastic tube from the bottom of your unit to where it terminates (often a floor drain or pump). Ensure it isn’t kinked, clogged with debris, or frozen if it runs through a cold space.

Step 3: The ‘Reset’ Button – When and How to Use It

After you’ve fixed a potential issue (like cleaning a filter or clearing a vent), you may need to reset the unit. The simplest way is to cycle the power by unplugging it for a minute or turning off the breaker. Some models also have a “Reset” button on the front panel. Only use the reset after addressing the potential cause of the error code.

Proactive Care: Your Best Defense Against Downtime

The best way to deal with a navien water heater won’t turn on situation is to prevent it from happening in the first place. This is where your proactive navien water heater won’t turn on care guide comes in. Following these best practices ensures reliability and efficiency.

Annual Descaling: The Secret to Longevity

If you live in an area with hard water, mineral scale (calcium and magnesium) builds up inside the heat exchanger. This forces the unit to work harder, reduces efficiency, and can eventually cause overheating or flow restrictions.

Descaling involves circulating a vinegar or specially designed solution through the unit using a small pump. While it’s a DIY-able task for some, many homeowners prefer to have a professional handle this annual service to ensure it’s done correctly.

Sustainable Performance Through Maintenance

Keeping your Navien running at peak performance is the most eco-friendly navien water heater won’t turn on strategy there is. A clean, well-maintained unit uses less gas and electricity to heat your water, lowering your carbon footprint and your utility bills. This is one of the key benefits of navien water heater won’t turn on prevention—you save money and help the environment.

When to Put Down the Tools and Call a Professional

Your safety is the top priority. While the steps above are safe for most homeowners, there’s a clear line where professional expertise is necessary.

Call a licensed and insured technician immediately if:

You smell gas. Leave the area immediately, do not use any electronics, and call your gas utility from a safe distance.
The issue involves internal electrical components or wiring.
You suspect a faulty gas valve, control board, or other major part.
You’ve completed all the DIY troubleshooting steps and the unit still won’t turn on.
You’re uncomfortable performing any of the steps listed in this guide.

Frequently Asked Questions About a Navien Water Heater That Won’t Turn On

Why does my Navien water heater click but not turn on?

That clicking sound is typically the spark igniter trying to light the gas. If it clicks but doesn’t fire up, it points to an ignition failure (like Error E001). The most common causes are an interrupted gas supply or a dirty flame sensor that can’t detect the flame, telling the unit to shut off the gas for safety.

Can I reset my Navien water heater?

Yes. The easiest and safest way to perform a “soft reset” is to simply turn off the power to the unit, either by unplugging it or flipping the circuit breaker. Wait for about 60 seconds, then restore power. This forces the internal computer to reboot and can clear temporary faults.

How do I know if my Navien flow sensor is bad?

The most direct sign of a bad flow sensor is the E110 error code appearing even when you have strong water pressure and have already cleaned the inlet filter. Other symptoms include the heater turning on and off randomly during a shower or failing to ignite at all, despite water running through the pipes.

How often should I service my Navien tankless water heater?

We recommend a professional service once a year. This service should include a full inspection, cleaning of all filters, and most importantly, descaling the heat exchanger, especially in areas with hard water. As a homeowner, you should check the inlet filter every few months.

Troubleshooting your Navien water heater can feel intimidating, but by tackling it logically—from the simple external checks to the more detailed internal ones—you can solve many common issues yourself. You’ve learned the most common culprits, how to decode your unit’s messages, and the critical importance of regular maintenance.

Remember to always prioritize safety. By following this guide, you’re not just fixing a problem; you’re becoming a more informed and empowered homeowner. You’ve got this!

Stay safe 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.