Noritz Tankless Water Heater Problems & Error Codes [Why+ How To Fix]

This is a complete guide on Noritz tankless water heater problems and error codes. Here, we are going to explore:

  • Noritz’s common problems that you face over-time
  • Error codes that flash during operation
  • And other tankless water heater-related issues

Mostly, you can simply fix your Noritz water heater issues by resetting your water heater.

Noritz tankless water heater problems

However, we identified the culprits behind the issues and explained the root source of the error codes. So, keep reading to resolve them and enjoy an on-demand hot water supply without calling professional help.

Table of Contents

Noritz Tankless Water Heater Problems And Error Codes [Solved]

From this guide, you will know how to diagnose the most common troubles of your Noritz tankless water heater with flashed error codes and fix them easily. So, let’s get started right here.

1. Heater Not Turning On/Keeps Shutting Off

You’re trying to turn on your tankless heater but the system isn’t responding. This is one of the listed problems with your water heater. In this case, a tripped circuit breaker is the main culprit behind the issue with an electric unit.

Noritz tankless water heater not turning on

Typically, the Noritz water heater has been designed to trip the circuit for safety precautions. However, mostly the circuit trips because of the following factors:

  • A Loose or bad electric wiring
  • Or, worn-out breaker.
  • No gas in the unit
  • And, a low flow rate

On the contrary, your gas water heater keeps shutting off if the gas valves aren’t fully opened. Because your water heater requires an uninterrupted gas flow, the minimum flow rate should be (O.5 GPM). 

How To Fix:

In this case, inspect the wiring line for any loose or broken connections. For a loose connection, tighten it enough. In case of a tripped circuit breaker, simply turn it to the ON position.

When there is no fault in the lines but your breaker trips, we suspect the breaker is broken or worn out. In this case, you’ll need to replace the circuit breakers.

replace the  tripped circuit breaker

And, for a gas unit, ensure the gas valves are fully open to supply enough gas to the unit. So, back to the fuel delivery system.

If you identify air trapped in the gas lines, purge it out of the water heater lines. In the below part, we’ll instruct you on how to bleed out the air. 

2. Unit Fails To Ignite

When your tankless water heater attempts to ignite but fails.  This is a common problem with a tankless water heater. In this case, the following leading reasons are mostly responsible for not igniting your unit. 

Noritz tankless water heater unit fails to ignite
  • Reversed Plumbing
  • Air in the gas lines
  • Dirty water drain valves
  • Too low gas pressure 

In simple words, all these reasons prevent the flame from igniting.

How To Fix:

For cross-plumbing, we suggest you inspect the hot and cold water lines. Your heater won’t ignite if the plumber incorrectly installs the hot water lines to the cold water lines. So reinstall the lines correctly. Make sure the water drain valves aren’t dirty. 

Next, regarding air in gas lines, bleed out the air from the system. It is very simple to purge the air from your water heater.

Watch the below video on how to remove air from the gas lines. If the bleeding doesn’t permit your heater to ignite, check the gas pressure.

To do so, you should call an expert plumber to handle and resolve your low gas pressure issue.

3. Power Is Off But Gas Combustion On/ Error E-10

Your tankless water heater’s power is off but the combustion is going on. This inconsistency indicates an uneven output. In this case, you will get error code 10 on your remote.

Basically, it may happen due to left-over materials and objects like oil and grease on the burner which are the common villains to display an error code 10. Because the storage of fuel is still burning even after the unit is turned off.

How To Fix:

If you’re having issues with your water heating recirculation process, apply the below tips to solve it.

First, look for foreign materials such as oil and grease, on the burner. If you find any leftover objects, carefully remove them from the unit. Also, make certain that there is no leftover material after each use.

Secondly, verify the exhausted flue for blockage.

Thirdly, to reset the code, try to maintain the water temperature difference between 10 °C. If your heater is still burning, turn it off and wait 60 seconds before turning it back on. Finally, you will get the solution.

4. Heater Not Heating/ Error Code-11

Your Noritz tankless water heater isn’t firing up to heat the water because of the following culprits. For example; 

  • Insufficient gas supply
  • Inadequate airflow
  • Loose ignition plug
  • Debris in the ignition plug
  • And, dirty burner

So, the mentioned points are the common reasons that prevent your water heater from igniting. Regarding ignition failure, you’ll get error code 11 until you solve the issues. 

How To Fix:

To heat up your heater, make sure your heater propane tank is full and there is enough gas pressure in the gas meter. Also, ensure that the gas supply is on and there is enough gas in the unit.

Therefore, check your gas pressure. If needed, call your plumber to test the gas pressure and check the spark. 

Secondly, your water heater won’t ignite if the gas and water valves aren’t fully opened. So, ensure the valves are opened fully. 

Now, verify the gas flow is working properly. Because the unit requires continuous gas flow to function properly. Sometimes, the gas meter line may be cut off due to insufficient gas supply. Then you won’t have any hot water. So, check it. 

Thirdly, the igniter senses flame to ignite the burner. But over time, it may be rusty or filthy. So, check it and carefully remove the dust and debris from the igniter with sandpaper or a soft brush. Tighten the ignition plug properly. 

When this effort doesn’t go well, we bet that your igniter pack has been defective. So, replace it ASAP. 

Fourthly, your burner plays a vital role in the heating process. If you notice your burner isn’t igniting properly, clean it. 

Even after cleaning, if your water heater isn’t heating up, replace the burner assembly with a working one. Hopefully, you won’t see the error code E-11 code again and your heater will start heating.

5. Burner Isn’t On/Burner Won’t Ignite

Your tankless water heater burner can’t ignite because of the following leading reasons: 

  • The gas supply isn’t enough
  • Closed gas valve
  • Loose/ dirty Ignition plug
  • Or, Dirty burner 

Generally, when the water flow enters the unit, the gas valve opens slightly. And then, the igniter senses a small flame to ignite the burner which heats the water.

So, it is impossible to ignite the unit without a proper gas supply. Plus, the improper size of the gas meter for the heater may cause the burner not to turn on. 

Secondly, a loose igniter plug is the next culprit that prevents your burner from lighting up. Furthermore, this could occur as a result of coating carbon buildup over time.

Lastly, the Noritz water heater burner won’t light if the burner gets dirty itself by dirt and debris, fuel residual. You can inspect the case through the viewport. 

If you notice the flame is inconsistent or yellow, we confirm that the burner has been dirty.

How To Fix:

To turn on the burner light for the first problem, we suggest you inspect whether the gas valve and gas supply are working properly.

Also, ensure that the gas supply valves are open for continuous gas supply. Check the gas pressure. We have already explained in the above section what to do for gas issues. In case of a defective gas valve, replace it. 

Next, if you notice the light is yellow or inconsistent, clean the burner before turning it back on. While cleaning your burner chamber, use an air compressor to blow away the particles like debris, oil, and grease from the burner chamber.

You can also read our ultimate guide to troubleshooting why Noritz tankless water heater burner light is not on.

Whatever proper maintenance is the key to keeping your heater’s burner fit for operation? So, clean your burner assembly after 3–4 months. Finally, the burner light will turn on.  

6. No Hot Water/ Error E12

Once you turned on the hot water faucet but there was no hot water to use with the taps. You experience this common trouble over time. In this case, Noritz tankless water heater throws error code 12.

A low flame or flame failure is mostly responsible for this problem. Basically, you’ll face a hot water issue with your water heater when the heater can’t detect the flame. However, there are mentionable reasons behind the issue.

  • Improper temperature setting
  • Partially open hot water fixtures
  • Don’t fully open the gas and water supply valves
  • Or, a frozen pipe 

When your gas heater faces a lack of gas and airflow, your water won’t heat properly.

Similar to error code 11, the igniter is falling and then showing error code 12. In fact, Error code 12, indicates that the unit has a weak flame that is not enough to heat your water.

How To Fix:

To fix hot water issues, do the following checks before calling professional help. Disconnect your power. Start your investigation with the gas and water supply valve. Make sure they are fully opened.

If needed, turn the water supply valve to the ON position. Then, check if water is supplied to the unit. Now, check if you set the temperature correctly. Set your user manual’s recommended temperature.

Inspect if the hot water fixtures are sufficiently open. You won’t get available hot water with your water heater unless you open the hot water taps fully.

After that, check whether the water drain valve filter is clogged. If it gets clogged, unclog it. Now, if you don’t see any error code, just open the shut valve. (Also inspect the error code 11 history.)

Lastly, we recommend flushing or draining your water heater periodically. Don’t overlook the power button. Check if you’ve turned it on. 

Hopefully, your problem will be solved. If it doesn’t, you can check out the video to fix the water hot issue.

Also, check out our comprehensive guide on Noritz tankless water heater with no hot water where we have explained every troubleshooting step to get hot water from your water heater.

7. Failed Thermal Fuse/Error Code14

Noritz tankless water heater thermal switch is a safety element. This element fails due to the following reasons and displays an error code 14.

  • Scaled or dirty heat exchanger
  • Restricted airflow

How To Fix:

Find the white corded thermal switch that is wrapped around the heat exchanger. If it gets dirty, clean it carefully but if it is broken, replacement is the best solution to remove error code 14.

Next, when the switch is fine, check out the water quality and sediment that can clog the heat exchanger. Flush the scaled heat exchanger. You can use a scale remover.

Ensure the unit has no airflow restriction in the vest system and there is proper gas for combustion.

If the cleaning effort can’t solve your issues, eliminate the trouble by replacing your heat exchanger with a new one.

8. Too Hot Water/Error code16

When you experience excessively hot water from your Noritz water heater, we suspect that you’ve set the temperature too high, probably at 125 degrees F. Plus, the possible causes behind the trouble are:

  • Improper temperature setting
  • Broken temperature sensor
  • Shorted heating elements
  • Sediment build-up
  • Improper adjustment of manifold pressure 

How To Fix:

Resetting your unit will be the best reply to solve the high outlet temperature issue. unplug the unit and wait 20-30 seconds.

Then, just plug it back on to disappear the error code 16. If your problem isn’t solved yet, go for the next troubleshooting steps.

Secondly, we recommend you set your desired temperature. You can easily adjust the water temperature by turning Up and Down the temperature dial controller.

Bear in mind that if it is set too low, the setting will exceed or the outlet temperature will reach abnormally too high

Thirdly, regarding sediment blame, flush and descale your water supply line routinely with vinegar, descaler or use a water softener.

Finally, make sure you have adjusted the manifold pressure as per the manual guide.

But in case of a broken temperature sensor or heating element, replace them ASAP. 

9. Tripped High-Limit Switch/Error Code 20

 The switch is a safety switch like the thermal fuse. The diagnostic code 20 will pop up on the display due to a tripped high-limit switch.

Unfortunately, when the water temperature level reaches above the recommended level at 176°F to 205°F, the high limit switch will trip.

And then it cuts electric power for the whole unit. In fact, your high-limit switch gets tripped to prevent further damage to your water heater.

Plus, a clogged heat exchanger is responsible for tripping the switch. Because a scaled heat exchanger can’t transfer the heat into the water. As a result, the heat transfers to other parts of the heater that cause overheating.

Nonetheless, the problem was caused by a blockage in the venting system and a loose wire connection of the high-limit switch.

How To Fix:

You can simply resolve error code 20 by resetting your water heater. If it doesn’t bring any luck, check whether the issue is with your high-limit switch. If it is broken, change it.

In other words, descaling your heat exchanger would be the best reply. But if it is out of working condition, you need to replace it.

lastly, don’t forget to ensure that there is no blockage and loose wiring in the high-limit switch.

Note:  High heat is the root cause of this problem. Hence, if you can’t solve the overheating issue, the error code 20 will flash repeatedly. 

10. Condensate Drainage Issue/Error Code 29

Typically, your Noritz water heater flashes error code 29 for a blockage in the condensate line or improper condensate drain piping.

Indeed, a tankless water heater has a special drain line equipped with a neutralizer to reduce the condensate. But an incorrect or blocked drain line can cause the burner to flood.

How To Fix:

To remove drainage troubles, remove any debris from the container and the drain line.

If you aren’t good at checking the overall process, call an expert plumber. He will check to ensure whether the condensate draining line is obstructed and routed properly. 

11. Leakage Issue/ Error Code 45

Noritz tankless heater’s water leak is a common problem. In this case, luckily, your unit will display an error code-45 which means excessive moisture or water has been detected in your heater.

The following culprits are mostly causing internal water leakage.

  • Hard Water or accumulated sediment
  • High Water Pressure
  • And, incorrect water pipe installation
  • Improper venting system 

Whatever the problems, you need to know how to prevent or solve leakage problems. 

How To Fix:

We highly suggest you follow the below steps to repair your tankless water leaks.

  • Shut off the cold water supply valve
  • Inspect for water leaks and moisture. Regarding leaks, service is required.
  • If you don’t find any visible leakage issue, reset your water heater by just unplugging the unit and waiting for 60 seconds.
  • Now, plug it back in. After resetting successfully, the error code will be disappeared.

But if the error code repeats, don’t wait but contact a professional plumber for rechecking the troubleshooting.

12. Fluctuates Water Temperature

Water temperature fluctuation is another common problem with a tankless water heater. Basically, you will face a reduction in water temperature unless you set the right temperature as per manufacturer manuals.

Plus, your water temperature will fluctuate if the water filter has been clogged by dirt and debris.

How To Fix:

Make sure you have set the water temperature between 115°F to 120°F.To adjust the desired temperature, turn the UP and Down button on the controller.

Next, if needed, clean the water filter by the following procedures.

  • Turn the water supply valve to the off position and open the hot water fixtures.
  • Take out the inlet and outlet drain plugs from the lower part of the unit. Place a bucket right below the plugs to hold residual water.
  • Remove both the drain valve and filter from your water heater.
  • Apply a brush to clear out all the dirt and debris from the drain valve. And then, wash the valve with clean water.
  • After that, brush up completely, and reinsert the filter.

After you have cleaned both parts, replace them and close the drain plugs. Close all the hot water taps.

Now, open the water drain valve and ensure that there is no leak with the drain plugs and water drain valve. Finally, your heater will be ready to run again. 

13. Malfunctioning Circuit Board/Error Codes 71 & 73

You can’t operate your water heater without a properly functioning circuit panel. When it starts maltreating, luckily, the faulty codes 71 and 73 appear on the remote control for either a faulty or damaged circuit board.

In simple words, error code 71 means that the gas valve drives the circuit abnormally. Again, if your circuit fails, the gas valve will not function. This mostly occurs when –

  • Wrongly installed a new circuit board
  • Powered up from a backup battery, solar power, or generator.
  • Or, voltage is not stable.

On the other hand, an issue with the circuit board settings is responsible for flashing error code 73. When power is supplied to the unit, changing the jumper connection and DIP switch can trigger your circuit board program. 

However, both the displayed faulty codes are related to a malfunctioned circuit panel. Now, you need to know how to fix it.

How To Fix:

To diagnose the error code 71, we highly suggest you test electrically to determine whether the gas valve or circuit board is responsible for throwing the error code.

A functional gas valve should receive 14–16 volts DC during operation. If you don’t get the voltage with the gas valve, be sure the circuit board is faulty. So, to avoid such an unstable voltage issue, you can use a power surge protector.

Secondly, to fix 73 code-related issues, first, program your circuit board functionally as mentioned in the user’s manual.

Then, changing the jumper wire, and inspecting the DIP switch setting will solve your problem.

Finally, we recommend that you shut off the power of the unit and wait for 30 seconds. Now, plug it in again to reset the displayed code.

Remember: If you see the codes persist repeatedly, changing the circuit board would be the best option to remove error codes 71 and 73.

14. Remote Control Issue/ Error Code F-76

A functioning remote controller is a must for operating your water heater properly. Normally, it breaks down the communication between two tankless water heaters when using the Quick Connect Cord.

However, the error code F76 involves a multi-system communication error. 

This may occur if two remotes are hooked up to operate two Quick Connect water heaters. Anyway, this isn’t a major problem at all.

How To Fix:

You can easily solve the problem by using one remote control to operate the water heaters. Ensure only one remote is connected when you are operating two tankless water heaters. Plus, check for loose wiring.

If the error code persists still now, call an expert electrician for a detailed inspection.

15. Gas Combustion Problem/ Error Codes 90 & 91

Improper combustion happens when air and fuel get mixed. Fortunately, the faulty codes 90 and 91 messages that your heater is going through abnormal combustion. 

In a true sense, while E90 stands for abnormal gas combustion due to an improper air, gas, and venting system, E91 indicates you’re feeding the incorrect type of fuel. As a result, your unit isn’t burning properly.

Plus, the error codes 90 and 91 poop up due to the reasons listed below. 

  • The unit isn’t receiving enough gas supply
  • Restricted exhaust venting system
  • The fan motor has been obstructed by dirt & debris
  • Incorrect DIP switch setting for elevation pipe size.
  • Improper setting Manifold Switch

How To Fix:

To make sure the gas valve is fully opened, turn the gas valve counterclockwise or gas won’t flow fully to the unit. If necessary, inspect the exhaust vent and clear any obstructions there.

Regarding a dirty fan, disassemble the unit to get the fan and clear out dust and debris by compressed air or degreaser.

Ensure, you’re fueling up the unit with the right type of gas to the unit. To verify the operation, have a look at the rating plate. You should feed it demand propane or natural gas. Don’t ignore the color of the flame, it should be blue. 

Lastly, verify you have set the DIP switch, and don’t forget to adjust the professional manifold pressure switch according to the owner’s manual for elevation, pipe size, and length.

Note: Also check and clear out the fan, burner, and heat exchanger routinely. Unless you are experienced enough, hire a professional to troubleshoot and repair it.

16. Making Loud Noise

Noritz tankless water heater making a slight noise is a common issue during operation. But, when it makes a loud noise, such as vibration, it is a matter of concern. This problem may arise because of

  • A dirty flow sensor and Loose parts. 
  • Sediment build-up
  • Internal Water Leaking
  • Clogged fan
  • And, water pressure fluctuations.

Whatever the issue, we strongly advise you to investigate the root cause of the loud noise. 

How To Fix:

For a dirty flow sensor, turn off your heater. Disassemble it and ensure that the sensor is dirty. If it gets dirty, clean it and replace it in the right position.

Then, turn on the gas valve and reconnect the power to run the heater again, and slowly pressurize your heater. But if the noise comes from the unit, don’t ignore it to flush out the buildup of sediment in the heater.

While identifying any loose parts, take a proper wrench and socket to tighten them. It will save you from great damage further.

Plus, recheck whether the water lines are secured in their place, such as—copper for copper and metal for the metal pipe. Don’t forget to inspect for water leaks.

Check that the water valve is fully open, otherwise, a restricted valve can cause intolerable noise. Make sure the blades of the fan are dust free. 

Finally, you can consider installing a spacer pipe or hammer arrestor close to the water valve to reduce loud noise.

You can also read our well-proven guide on why Noritz tankless water makes loud noise where you will come to know how to resolve your heater’s noise problems. 

17. System Overloaded Issue

Typically, a tankless water heater has a flow capacity. The rate gives you a clear idea of how much hot water can be used at a time.

But when your water heater has to go over the rate, it will encounter overloading issues. Suppose, you have just completed your shower but someone is right there.

At the same time, someone may have opened hot water faucets. As a result, it will restrict the water recirculation process and take time to heat the water.

And then, many customers think a tankless water heater has a limitation on its ability to supply hot water simultaneously.

In some cases, the overloading system can stop the heater entirely. However, you can simply fix the problem.

How To Fix:

First of all, try to avoid overloading issues by reducing the demand for simultaneous hot water applications.

Plus, you can consider upgrading your tankless water heater with a higher capacity by adding a second unit to the existing one.

Though it is costly, it would be a great investment, and you won’t face any more issues getting sufficient hot water for your family.

How To Reset Noritz tankless Water Heater

When your Noritz water heater goes into trouble and flashes error codes frequently, find out the root causes and fix them specifically.

Then, you can simply reset your water heater to resolve most of the trouble. It may save you huge money and time. Follow the instructions to reset.

Disconnect the power and locate the reset button. It is usually located on the side or front of the unit. After getting it, make sure the reset button is in “Reset Mode.” 

In this case, you may need to press the reset button once more to bring it back into reset mode. And then the light will turn red to green. After the step is done successfully, wait for 10 seconds.

Turn on the clockwise knob to the highest setting and wait for 10 seconds again. Finally, plug the power line into the electric outlet. Now, the reset has been completed.


Why does Tankless water take a time to heat the water?

A tankless water heater takes much time to heat water due to the long distance between the pipe and the shower tap. So, you can install a recirculation tank between the unit and the shower.

How to find out the history of the error code of a tankless water heater?

Turn the power button On. Then, hold down the Up and Down Arrow together and press on them until the unit is displayed 003. Finally, press the Up button first and then the Down button to get the error codes one by one.

What does error code 51 mean by Noritz water heater?

The E51 will blink on the remote controller when the gas manifold solenoid is at risk. Don’t DIY, but you should call an expert to fix this complex problem.

Why does my water heater flow discolored and smelly water?

You experience smelled or discolored water because of building up sediment and minerals in water supply lines. Plus, flushing due is also a reason behind the hits. Flush and clean your bathtub and basin periodically.

What is the ideal temperature setting of a Noritz tankless water heater?

120 degrees Fahrenheit (50 Degrees C) is the default and ideal temperature setting for a tankless water heater. If needed, you can adjust it as recommended. 


Now, it is worth mentioning, this is an ultimate guide on your Noritz tankless water heater troubles and error codes. Because we have explained nicely how to troubleshoot your Noritz’s issues. 

From this guide, you have also got every solution to your tankless water heater’s problems. Anyway, operate your water heater under regular maintenance to avoid such unwanted issues.

So, follow our Noritz water heater troubleshooting guide whenever you encounter any trouble with your Noritz water heater. And, don’t hesitate to share your thoughts and comments with us.

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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