Noritz Tankless Water Heater Problems And 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
  • Proven fixes to erase the codes and fix any heater issues. 

Mostly, you can simply eliminate most of the Noritz water heater issues by resetting your water heater. If that doesn’t resolve the problem, you need to identify the culprits behind the issues and then head to troubleshooting action.

Noritz tankless water heater problems

So, if all that sounds exactly like what you are looking for, let’s dive in!

Table of Contents

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

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 that prevents the heater to turn on.

Noritz tankless water heater not turning on

Besides this, your Noritz tankless water heater won’t turn on or fails to stay on because of the following factors:

  • Loose or bad electric wiring.
  • Or, worn-out breaker.
  • Damaged power cord connection
  • Non-functional electrical outlet.
  • Low water flow 

On the contrary, your tankless water heater will keep shut off if there is an interruption in the gas supply to the system. This would be related to the gas valves that aren’t fully opened. 

At times, the gas supply is being cut off to the unit, or not enough fuel in the tank if you have propane operated water heater. It could also be obstructions in the gas line that causes the unit to shut off. 

How To Fix:

First off, inspect the wiring connection to your water heater 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. Plus make sure you’ve plugged your water heater into a well-functional power outlet. 

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 your circuit breakers.

replace the  tripped circuit breaker

After fixing the electric supply issue, head to verify the gas and water pressure of your water heater. For instance, check out the followings:

  • Ensure the gas valves are fully open to supply enough gas to the unit. Also, make sure the gas valves are in perfect working order.
  • If you have an LP tank, verify there is sufficient fuel in the tank. If needed refill it. 
  • Inspect the gas line for any obstructions and remove it. Straighten the bent gas line. 
  • If you identify air trapped in the gas lines, purge it out of the heater lines. Call a professional if you find it difficult to purge the air from the gas line. 
  • Finally, check for obstructions in the water supply lines. Remove the obstructions to ensure the minimum required water flow rate.

2. Unit Fails To Ignite/ Error Code 11

When your tankless water heater attempts to ignite but fails, this is a common problem with a tankless water heater. Whenever your Noritz tankless water heater fails to fire up, the controller triggers this issue and displays the error code 11. 

Noritz tankless water heater unit fails to ignite

When this happens, you won’t get the hot water as before. Anyway, to fix the issue, it’s essential to track down the leading reasons that are mostly responsible for not igniting your unit. 

  • Insufficient gas supply
  • The gas valve isn’t fully open
  • The fuel tank is empty or you’re using the wrong type of fuel.
  • Scale build-up on the ignition rod
  • Plugged up burners 
  • Blocked venting.  

How To Fix:

Here’s all you need to do to fix the error code 11 from your tankless unit:

Step #1: Start by inspecting the gas valve of the heater. Make sure it is fully open.

Step #2: Check out the fuel amount in the tank and refill it if needed. Also, you need to ensure that you are using the right type of fuel for ignition.

Step #3: Next check the gas pressure for your unit using a gas monometer. If you find it difficult, call your plumber to test the gas pressure and check the spark.

Step #4: Look for any obstructions in your venting system. You need to ensure a fluent air flow to your unit. Clean out the vents properly.

Step #5: Finally, inspect the igniter rod. It may be rusty or filthy. Remove the dust and debris from the igniter with a sandpaper or soft brush. Plus, 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.

Step #6: Above all, your burner also plays a vital role in the ignition process. If you notice your burner isn’t igniting properly, clean it. 

Even after cleaning, if your water heater isn’t firing 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.

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:

Here are some simple fixes you can apply to diminish the error code 10 from your tankless water heater:

  • First off inspect the burner and check for remaining foreign materials. Carefully remove them from the unit. Also, make certain that there is no leftover material after each use.
  • Next, verify the exhaust flue for blockage.
  • When done, now it’s time to reset the code. Turn the unit off and let it reset for 60 seconds. Then turn the power back on. 
  • Above all, if your water heater has a recirculation system, try to maintain the water temperature difference between 10 °C. 

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

Your Noritz 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, a dirty burner 
burner won’t ignite

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 line is in perfect working order.

Also, ensure that the gas valves are open for continuous gas supply. Check the gas pressure. In case of a defective gas valve, replace it. 

Next, inspect the ignition plug for any carbon deposits. Use 100-grit sandpaper to clean the clogged element.

 After cleaning, check the connectors of the flame-sensing rod and ignition plug to ensure they are secure and tight. 

Finally, check the burner flame through the viewport. 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.

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.  

5. No Hot Water

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.

Basically, you’ll face a hot water issue with your water heater when the heater can’t detect the flame properly. However, there are mentionable reasons behind the issue.

  • Improper temperature setting
  • Partially open hot water fixtures
  • The gas and water supply valves aren’t fully open 
  • Or,  frozen water lines 

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

How To Fix:

To fix hot water issues, do the following checks before calling professional help.

Disconnect the heater from the power connection. Start your investigation with the gas and water supply valve. Make sure they are fully opened.

gas and water supply valve fulley 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. 

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, check out our comprehensive article where we have explained every troubleshooting step to fix no hot water issue from your water heater.

6. Weak Flame/ Error Code 12

If you have Error Code 12 on your Noritz tankless water heater, it is signing you a flame-loss issue on your unit. In such cases, the flame was ignited but it is not strong enough or gets extinguished after short igniting.

Whenever you will have error code 12 on the control panel, you won’t find the outlet water hot enough as your expectation. 

Several factors would lead to this error at the Noritz unit. Such as:

  • Filthy flame sensor rod and ignition plug
  • Interruption in gas supply
  • Blocked venting system

How To Fix:

Here’s all how you will go about low flame or flame failure in your tankless unit:

First up, you need to ensure that there is sufficient airflow throughout the system to continue the combustion. For instance, inspect the venting and clean it if you find any blockages here.

Next, make sure the gas valve is fully opened and the gas pressure in your tankless unit is at the recommended level. 

Finally, locate the flame sensor rod and ignition plug. The best chance is they are covered by shoots and debris. Without worrying, take sandpaper and rub the sensor body. 

If just cleaning doesn’t bring any luck, be sure they are defective and you need to replace the defective parts. 

7. Failed Thermal Fuse/Error Code14

Noritz tankless water heater thermal switch is a safety element. Basically, when this safety element fails, the controller triggers the malfunction and displays an error code 14.

Before moving to the troubleshooting, let’s mention all the factors that lead to  thermal fuse failure:

  • Obstructed airflow
  • Plugged-up heat exchanger
  • Or broken thermal fuse is the culprit itself.

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 vent 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

While operating the water heater, it’s a quite common phenomenon that the water temperature is too high. In such case, the best chances are you are getting error code 16 on the control display, 

Error code 16 on the Noritz tankless water is a clear indication of the excessive outgoing water temperature of the unit. Whenever you will encounter error 16 on your Noritz, we will first recommend shutting off the heater right then to prevent scalding. 

Now find out the responsive factors for this issue. We suspect that you’ve set the temperature too high, probably at 125 degrees F. Plus, the possible causes behind the trouble are:

  • Plugged-up heat exchanger
  • low water pressure
  • Improper adjustment of manifold pressure 

How To Fix:

First off, verify the set temperature on the thermostat to see whether it is set too high. If so, adjust the water temperature with the Up and Down temperature dial controller.

Then, hard reset the heater by unplugging it from the power connection. Wait for one minute before plugging it back in to disappear the error code 16.

If still the problem persists, you may have low water pressure in your unit. Increase the water pressure from the water shut-off valve. Also, inspect and clean it water filter as well.

Also, 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. If you are not getting it enough, call a professional for your assistance. 

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, the high limit switch will trip and cuts the electric power for the whole unit. By doing so, it helps to prevent further damage to your water heater.

In most cases, the problem is related to the heat exchanger when it is clogged with limescale, and for why it’s getting hard to transfer the heat into the water. As a result, the heat transfers to other parts of the heater that is causing overheating. 

Nonetheless, the problem may also be caused by a blockage in the venting system and a loose wire connection of the high-limit switch. Plus, at times, the malfunction of the hi-limit switch is the culprit itself for error code 20 on Noritz

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. Fix the loose wiring in the 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 air blockage in the system.  If so, unclog the exhausts and air intake using a vacuum cleaner. Also, clean out the air filter screen. 

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:

  • First up, inspect the neutralizer for any blockages and clean it to ensure proper draining.
  • Then ensure the condensate drain line is routed properly.
  • Finally, look for any obstruction in the water level sensor that leads the water to the incorrect level. Clean it or if needed replace the broken sensor. If you aren’t good at checking the overall process, call an expert plumber.

11. Leakage Issue/ Error Code 45

Noritz tankless heater’s water leak is a common problem that users mostly face. 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.

  • Bad water condition 
  • 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.
  • For instance, look for loose connections in the water pipes and fittings. Secure and tighten them enough.  Also, the pipe may be blocked by dirt & debris. Just remove the obstructions.  Check for water pressure in your water heater and adjust it to the recommended level. 
  • Then ensure the proper installation of the venting systems. 
  • 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 45 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.

fluctuates water temperature

Plus, it may occur due to low water pressure. If the water filter has been clogged by dirt and debris or at times due to incorrect plumbing, you will experience an ultimate drop in the water flow rate to the unit. 

How To Fix:

First up, 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, inspect the water filter and clean it through the following procedures.

Step #1: Turn the water supply valve to the off position and open the hot water fixtures.

Step #2: 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.

Step #3: Remove both the drain valve and filter from your water heater.

Step #4: Apply a brush to clear out all the dirt and debris from the drain valve. And then, wash the valve with clean water.

Step #5: After that, brush up completely, and reinsert the filter.

Step #6: After you have cleaned both parts, replace them and close the drain plugs. Close all the hot water taps.

Step #7: 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. 

If still, the problem persists even after cleaning the drain valve and filter screen, I bet you have a major issue with your plumbing system. For instance, you can call an expert to fix the issue.

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, Noritz tankless water heater error code 72 is mainly related to the abnormality of the flame sensor rod detection circuit. When the flame is sensed without a proper ignition sequence, the controller displays this error code. 

How To Fix:

To diagnose error code 71, we highly suggest you test electrically to determine whether the gas valve is functioning well or not.

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,  inspect the circuit and look for any damaged wiring. Especially inspect the flame detection circuit and replace it if needed.

But before handling the circuit board, we highly recommend ensuring that your unit is properly grounded. If possible, contact a professional for your assistance.

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. Multi-system Communication Error / 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 & 99

The faulty codes 90, 91, and 99 on Noritz tankless water heater are indicating the same error message that your heater is going through abnormal combustion. Improper combustion happens when air and fuel get mixed.

Plus, the error codes will poop up due to the reasons listed below. 

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

How To Fix:

First off, make sure the gas valve is fully opened. For instance, turn the gas valve counterclockwise. 

Along with this, check whether 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. Don’t ignore the color of the flame. It should be blue, signing you a proper mixture of fuel and air.

When done, inspect the exhaust vent and clear any obstructions there.

clean the  exhaust vent

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

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.

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:

Whenever you will experience a loud noise from your Noritz tankless water heater,  we strongly advise you to turn off your unit right then. Then, go through the following:

Fix#1: Disassemble the heater and inspect the flow sensor. If it gets dirty, clean it and replace it in the right position.

Fix #2: After that, identify the loose part from the heater inside. Take a proper wrench and socket to tighten them. It will save you from great damage further.

Fix #3: Double-check whether the water lines are secured in their place, such as—copper for copper and metal for the metal pipe. 

Fix #4: Verify that the water valve is fully open. Otherwise, a restricted valve can cause intolerable noise. 

Fix #5: If you suspect the noise is coming from inside due to sediment deposit, flushing is the only solution to resolve the issue. 

Tips: You can consider installing a spacer pipe or hammer arrestor close to the water valve to reduce loud noise.

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.

Most often, the overloaded system stops the heater entirely and you can’t expect to have hot water again until you have fixed the issue. 

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

Whenever you encounter any error code or any other issue on your Noritz tankless water heater, resetting the unit is one of the most effective processes to get rid of the troubles. 

But before moving to reset your Noritz tankless water heater, you need to locate the reset button first. But unfortunately, there is no built-in reset button in Noritz tankless water heater.

But don’t lose hope. Despite the reset button, there are a few more processes to reset your tankless water heater into the default setting. Here go you:

Step #1: Move to the circuit panel and locate the circuit breaker for your water heater.

Step #2: Flip the circuit breaker to the Off position.

Step #3: Just wait for 30 seconds.

Step #4: After that time, flip up the breaker to the ON position.

Step #5: Finally, turn on your tankless water heater from the power button. 


Why does Tankless water take 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 65 mean by Noritz water heater?

When the Noritz tankless water heater controller triggers an issue with the main flow control valve, it displays the error code 65. The best chance is the control valve has stopped functioning due to blockages or some internal mechanical failure. 

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.

Also, 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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