Noritz Tankless Water Heater Burner Light Not On [Reasons + Solutions]

The root reasons for your Noritz tankless water heater burner light not on are:

  • Insufficient gas supply.
  • Restrictions in the water supply line
  • Dirty burner
  • Insufficient airflow
  • Malfunctioning flame detector sensor 
  • Or, a loose ignition plug

Whatever the fact is, you can simply fix the issue by removing all the obstructions from gas and water supply lines to your water hearer. Also, clean your burner to turn it on.

noritz tankless water heater burner light not on

If the cleaning effort doesn’t work, check out all other villains like malfunctioning ignition plugs or flame sensors as we’ve explained below.

Noritz Tankless Water Heater Burner Light Not On [Reasons + Solutions]

Here, we’ll explore the culprits that prevent your Noritz tankless water heater burner from turning on and guide you on how to solve the problems easily.

noritz tankless water heater

But, before going to troubleshoot a tankless water heater burner that isn’t igniting, it is essential to know how the burner performs.

Note: You can also read how to fix Noritz tankless water heater no display.

How Does The Burner Of A Tankless Heater Work

The burner is a device that is designed to work automatically. As usual, when the water flow enters the unit, the gas valve opens slightly, and the thermostat measures the heat to produce hot water.

And then the igniter senses a small flame to ignite the burner. But, now the question is why is your burner not igniting? Let’s identify each reason regarding the problem.

1. Insufficient Gas Supply

This is the most common and number one reason for not turning on your burner. You can never expect to ignite your burner if no gas is flowing to the unit at all. It would happen due to any of the following reasons:

  • The gas supply is being cut off by the gas meter.
  • Not enough gas pressure for the unit.
  • Improperly sized gas meter or gas line. 
insufficient gas supply of noritz tankless water heater

Plus, your water heater burner won’t receive any gas if the gas supply lines get clogged or blocked. For instance, the accumulation of dirt, debris, insects, and rust in the gas lines as well as physical pipe deformation may be the culprits behind the issue. 


When there is any gas supply issue, first up verify whether the gas is being cut off from the gas meter. If so, contact your gas utility company.

Along with this, you need to ensure that the gas lines and the gas meter are sized up properly thus it would meet the total BTUs demand for your unit. 

Next, make sure that you’re using the right type of fuel for your tankless unit. If that is ok, check the gas pressure of your heater using a gas monometer. Go through the manual for your tankless model and adjust the gas pressure to the recommended level.

When done, inspect the gas control line or gas orifice and remove dirt and debris from there. 

[Remember, leaving a clogged gas line unrepaired may cause a risk that can lead to a very hazardous situation.]

noritz tankless water heater clogged gas line

Finally, head to the gas valve and turn it to the right position to let the gas flow freely. By doing so, your Noritz’s burner should light on to run your heater smoothly.

2. Water Supply Valves Are Closed Or Partially Open

It is one of the major reasons why your Noritz tankless water heater burner not coming on. Your burner won’t come on if the water shut-off valves are not fully open and there is any obstruction to the water-flowing path.

At times, the water flow rate to the heater drops down and ultimately the burner won’t ignite.


First off, verify whether the water supply is cut off to your house. If that is fine, inspect the water supply line and it should be free of debris. 

Turn on the water supply valves all the way. Also, check out the hot water fixtures and make sure they are sufficiently open.

Finally, measure the water pressure for your unit using a water pressure regulator. If the water flow is too low, I bet the flow sensor is the culprit now. Inspect the flow sensor and clean it properly. If needed, replace the bad flow sensor. 

3. Filthy/Dirty Burner

You can’t expect to turn on the burner if your burner gets dirty by dirt, dust, and fuel residual over time. Whatever, you can easily know if the burner has become filthy.

How To Test The Burner’s Functionality

You can visually check for flame and the burner functionality through the following method:

  • First up, set your desired temperature, and then pull out the cover access panel to your water heater.
  • Now, keep your eyes on the sight-glass to see whether the flame is blue. If you get the blue light, the burner is fine to stay lit.
  • But if you can see too low, inconsistent, or yellow flame there, be sure that the burner has been restricted and you need to clean it.


Whenever you detect the light is inconsistent, the burner must be cleaned. Here’s all how you will access and clean the burner assembly:

maintenance of the noritz tankless water heater burner

Step #1: Turn off the gas and electric supply to the unit.

Step #2: Disconnect the gas manifold connection from the wiring connection and remove the gas manifold to access the burner chamber. 

Step #3: Once you’ve revealed the burner assembly, it’s time to clean it. Take an air compressor and blow away the particles from the burner chamber.

We recommend cleaning your burner assembly every after 3-4 months to maintain the heater efficiency. Also, by doing so, you can always ensure a healthy burner flame. 

4. Insufficient Air Flow

Insufficient airflow is also responsible for preventing your burner from igniting. It is simply related to an interruption in oxygen supply to the burner assembly that prevents to light of the burner flame. 

Anyway, your heater may suffer from insufficient airflow because of the following reasons:

  • Clogged air filter screen
  • Blocked exhaust or air intake supply.
  • The vents might not be adjusted properly. 

Also, the build-up of larger particles of dirt, dust, lint, and unexpected objects in various heater parts is also a culprit for why the system will suffer a shortage of sufficient air to come on the light.


To fix the poor flow issue, first, ensure there is no condensation. Check the air filter for blockage. If it gets clogged, clean your air filter periodically.

To clean the filter screen, use a wire brush and remove the stuck particle. Then, clean it under running water and let it dry before installing. 

When done, inspect the exhausts of your tankless unit and look for any accumulated specks of dirt and debris there. Use a vacuum cleaner to suck up the debris and lint from the vents.

 Moreover, you can use a duct cleaner to clean the vent inside that is hard to reach. While doing so, be careful not to hurt the gas fitting or nearer parts of the filter during cleaning.

When done, hopefully, now, your heater will get enough airflow for burning properly. If it doesn’t work, then a faulty flame sensor is the next culprit behind the issue.

5. Malfunctioning Flame Detector

A flame detector is an essential element of a Noritz tankless water heater that is to detects the flame and keeps the gas supply line open to feed the fuel to the burner. But a defective sensor fails to detect the flame, and that’s why it doesn’t keep the gas line open to light the burner. 

noritz tankless water heater malfunctioning flame detector

Ultimately, the burner won’t light. The best chances are it doesn’t have a good connection with the igniter signal or it might be clogged by debris. At times,  the sensor is defective. 


When you confirm that the flame detector is jammed, it just needs a good cleaning. So, follow the below steps to clean your water heater flame detector.

  • Turn off the power of the heater and gas valve.
  • Remove the mounting screw.
  • Carefully remove the sensor.
  • Inspect it for clogging. If it has been dirty, clean it with an emery cloth. 

Generally, a faultless flame sensor provides a nice blue flame, but if it is burnt or defective, you will notice that the flame will be yellow or orange. If it happens, replace the flame sensor to get lighting with your burner.

6. Loose Ignition Plug

The Noritz water heater’s igniter plug helps to ignite the main gas burner. The process will interrupt once the plug gets coated with carbon deposit. 

noritz tankless water heater loose ignition plug

Also, the plug may be loose or not correctly installed at its position which causes the flame becomes feeble, small, or yellow. 

At times, you will have no light with your burner and don’t get hot water to use.


Apply the below step-by-step procedures to inspect and check the igniter components for loose connection:

Step #1: First, switch off both the electric and gas supply to the water heater.

Step #2:  Unscrew the front cover of the unit and keep the parts in a safe place.

Step #3: After that, disconnect the white connector to the ignition plug and flame rod. Now, remove the screws safely on the sides by using a Phillips head screwdriver.

Step #4: After unscrewing the nuts of the sides, pull out the flame rod and sensor. Be careful so that the gasket isn’t damaged as it is very fragile.

Step #5: Now, apply sandpaper to clean the carbon deposits from the flame rod and ignition plug.

After cleaning successfully, replace both the plug and the sensor in their right place. Place your gasket and secure the nuts tightly.

Finally, attach the white connectors to the flame-sensing rod and the ignition plug securely. Hopefully, your tankless unit will relight as usual. You can check out the video to replace your tankless water heater igniter.

Noritz Water Heater Error Codes With Burner’s Lighting Issue

Generally, your Noritz tankless water heater displays several error codes to provide warnings to solve the problems of the burner lighting issue. 

Here are some error messages that hint that something wrong is going with your burner and failing to ignite the heater. So, check them out.

Noritz Error Code No Reasons/causes Possible Solution
 Code-11> Indicates ignition/ flame failure or insufficient gas flow> Unobstructed exhaust vent and clean ignition plug and free from debris.
 Code-12> Weak flame by lack of gas or insufficient airflow low> Take the actions same as error code-11
Code-29> Problem with condensate drainage/ A blockage in the condensate drain line.> Make sure the condensation line is routed and unrestricted. If needed, call a professional.
 Code-90> Abnormal combustion is caused by an improper mixture of air and fuel.> Check gas pressures, venting length, dip switches, etc.

How To Light Up A Noritz Tankless Water Heater

Lighting up the tankless water heater properly is quite essential to continue the ignition process without any distraction. Also, it is needed if you are turning on the unit for the first time or have just completed the heater maintenance.

Anyway, follow the below step-by-step instructions to light up your Noritz Water Heater: 

Step #1: Before lighting make sure you’ve read through all the safety precautions mentioned in your Nortiz tankless water heater manual. It is highly recommended not to try to light up the burner by hand. 

Step #2: Start by turning off the electric and water supply to your water heater.

Step #3: Then, shut off the gas supply as well by turning the gas shut-off valve clockwise. Wait for 5-10 minutes.

Step #4: It will clear out all the remaining gas on the supply line.

Step #5: When done, turn on the gas shut-off valve. And then restore the power supply to your water heater.

Step #6: Set your desired temperature and your heater will light on. 


Where is the burner of a tankless water heater?

Normally, the burner part is located at the bottom line of the heater, just behind the access metal panel/cover. You can view the flame of the burner through the viewing port.

What does the burner assembly include?

Mechanically, a burner assembly includes together with the pilot burner orifice, a pilot burner gas supply tube, and a thermostat.

How does a tankless water heater operate with lighting?

After firing up, the gas valve slightly opens and then the igniter lights the flame. Then, the flame sensor detects the flame within 5-10 seconds and the unit starts operating the heater.

Why is my water heater igniter not igniting?

Mainly, the igniter ignites the gas. So, first, ensure that the igniter is getting enough voltage, if it gets so, but the igniter doesn’t spark, this hints that the igniter is defective, and should be replaced.

How to turn on my tankless water heater?

First, turn the gas shut-off valve to the ON position (Clock counter-wise). Next, simply, turn the electric breaker back on the power switch to start the unit.


At the end of the guide, we hope that you have got a clear idea of why your Noritz tankless water heater burner light is not on. It would be wise to take care of your heater and periodically inspect the viewport of the burner to see its excellent performance.

Whenever you will face ignition issues with the burner, follow our troubleshooting guide to fix them instantly.

Yet, if you have more questions regarding the burner lighting procedures, leave a comment below, and our expert will get back to you with the best solution.

About Phillip

Phillip is an HVAC guy & has convenient skills in the fireplace, heater, stove & other heating systems. He has been working and writing in this field for the last 5 years. He is really passionate about writing & share his expertise through his writing to help others. More about us.

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