Noritz Tankless Water Heater Troubleshooting – Guide You Want to know 2021

Noritz tankless water heaters exhibit numerical codes on the display screen when something is wrong.

Interpreting these codes and fixing them correctly is extremely important. Therefore, we are going to cover you today.

We know how infuriating it is when your heater suddenly stops working and shows a random code that you have never seen earlier. We are here to make things clear for you.

We will first enlighten you about how to take proper care of your unit and then discuss the common Noritz combi boiler error codes and how to fix them without employing professional service.

Knowing how to do Noritz tankless water heater troubleshooting can help you save a lot of time and money. So let’s take a look at Noritz error codes, what they mean, and how to solve them.  

noritz tankless water heater troubleshooting

How To Take Proper Care Of The Noritz Heater?

To keep your device in tip-top condition, you should purge the port valves by connecting hose lines and opening the relevant purge port valves.

If you are fully ready and have a safe ejection area, it should be an easy procedure and eliminate waste from your machine.

On the flip side, you can also take advantage of pure white vinegar to clean out the water now that you have purged its lines.

The manufacturer recommends various draining and flushing methods, so make sure to follow them when cleaning out your appliance.

No matter which method you choose, avoid using punitive chemicals during the cleaning procedure because they will lead to destruction.

After completing the cleaning process, turn your unit on again. Do it slowly to get rid of any trapped air from the heater.

Do it by locating a tap furthest away from the unit and activating it slowly to remove the air safely.

Error Codes And Noritz Tankless Water Heater Troubleshooting

noritz tankless lg

No Error Code

Sometimes the device does not function properly, but no numerical code is shown. It happens due to these problems:

  • If the display does not exhibit the preset temperature when the unit is running, confirm that the power voltage, circuit boards, and remote controller readings are according to the specifications. Also, examine the fuse and wirings of the unit.
  • If the fan does not operate when the warm water valve is opened, it means a water flow sensor is damaged, or the cold water thermistor detection is not functioning appropriately or set extremely high.
  • If the outlet water temperature is wrong, ensure the heat exchangers and hot and cold water thermistors are working correctly.  

Error Code 05

Problem: It means the time has come for the appliance to be serviced by a professional technician.

  • It is not an error code but a reminder that your heater needs servicing. Don’t reset your machine before service because it can affect your heater negatively.

Error Code 10

Problem: If the power has dropped or gas combustion is still occurring even after the heater has been shut off.

  • Look for external objects such as oil or grease on the burner that might still be burning after gas combustion has stopped. Shut the device off and then on to reset the Noritz tankless water heater.

Error Code 11

Problem: Ignition has failed in your appliance.

  • Check the gas pressure and confirm nothing is blocking the air supply. Eradicate the foreign objects from the ignition rod and also ensure the wires are not loose in the ignition.

Error Code 12

Problem: This error code indicates that the burner flame is extremely low and insufficient to heat the device, or the flame rod does not sense a flame.

  • Check the gas pressure and make sure nothing is preventing combustion. Clean the flame rod or sensor to remove debris.
  • If the flame rod cannot be cleaned and is defective, replace it.
  • Adjust the airflow to produce a good flame.

Error Code 14

Problem: This code tells you about the problem with the thermal fuse. It shows up due to the poor water quality and limited airflow. 

  • To resolve it, you should replace the thermal fuse. Sometimes, you may also have to change the heat exchanger and clean the entire heater.

Error Code 16

Problem: It specifies that the water temperature is extremely high.

  • This problem most frequently occurs because of hard water or scale accumulation, so you will have to perform a descaling process. To reset the error code later, disconnect the unit for 20 seconds and plug it back in again.

Error Code 20

Problem: It appears when the high limit switch has been turned on.

  • Check the high limit switch and replace it if required. Otherwise, you can descale the heater for Noritz tankless water heater troubleshooting.

Error Code 29

Problem: When these troubleshooting codes show up, the water level has surpassed the correct level because the water level neutralizer is not draining properly. 

  • Confirm the condensate drain line is accurately directed, and there are no blockages as well.
  • Furthermore, the condensate piping should be of the correct size and tilted correctly. 

Error Code 31

Problem: When this code displays on the screen, it means something is wrong with the inlet thermistor.

  • Change your inlet thermistor.

Error Code 32

Problem: The outlet pipe’s warm water thermistor has broken down.

  • The sensors have stopped working. Replace your thermistor.

Error Code 33

Problem: The heat exchanger thermistor has failed.

  • Replace the heat exchanger thermistor.

Error Code 45

Problem: There is a water leakage issue.

  • Shut off the water inlet valve and call a professional plumber if you witness a water leak. If the leak is not perceptible, disconnect the appliance for 30 seconds, plug it back in, and check if the code disappears.

Error Code 59

Problem: This code informs you about the low input BTU and combustion issues.

  • The gas combustion does not acquire sufficient fresh air, or the combustion products are not vented completely because of vent obstructions.
  • Eliminate the obstructions in the venting.
  • Clean dirt and debris from the burner chamber and fan motor.
  • Besides, adjust the unit for correct height elevation.

Error Code 61

Problem: It enlightens you about the failure of the fan motor.

  • Make sure the voltage coming into the fan motor is accurate.
  • If the voltage is not enough, replace the CB.
  • However, if the voltage is correct, you will have to change the fan motor.

Error Code 65

Problem: It shows up when the main flow control valve has failed.

  • Inspect the flow control valve for obstructions and replace it if required.

Error Code 66

Problem: There is an issue with the bypass flow control valve.

  • Check if there is a blockage in the bypass flow control valve and remove it. If it is still not working appropriately, replace it.

Error Code 67

Problem: It tells you about the faulty air-gas mixer.

  • Shut off the heater and after some time, turn it on.
  • If the error code persists, the problem is still there. Replace the air-gas mixer.

Error Code 70

Problem: It means the circuit board has malfunctioned.

  • Change the circuit board to get rid of this code. 

Error Code 71

Problem: The gas valve drive circuit is defective.

  • After consulting the Noritz hot water heater manual, you will get to know that this error code appears if the unit is attached to the battery backup, generator, etc. and if the current supply fluctuates.
  • Examine the current from the CB due to the damage.

Error Code 72

Problem: It indicates that the flame rod senses the fire without the ignition categorization.

  • Make sure your heater has proper grounding.
  • Inspect if the circuit board and flame detection circuit are damaged.

Error Code 73

Problem: The circuit board settings are incorrect. If you have replaced the dip switch or changed a jumper connection while the power was distributed to the device, this problem can occur. An incorrectly programmed circuit board can also trigger this issue.

  • Disconnect the unit for 30 seconds and then plug it back in. If the error code is still there, hire a technician for Noritz tankless water heater troubleshooting.

Error Code F76

Problem: It means there is miscommunication between your heaters (if you have more than one) that are linked with a quick connect cord. More than one remotes connected to the devices can instigate this issue.

  • Inspect the remote controls and confirm only one remote is working for various units attached.
  • To resolve troubleshooting codes, detach the machines for 30 seconds and then plug them back in.

Error Code 760

Problem: It informs you about the remote control problem.

  • Check if the wires are loose.
  • Check the remote controls and ensure only one remote is linked to several appliances.
  • If the code persists, disconnect the machine for 30 seconds and then plug it back in. 

Error Code 90 And 91

Problem: The gas combustion is abnormal.

  • Check airflow blockage and inadequate gas burning. Make sure the air/fuel mixture and gas pressure are accurate. Once the code is resolved, reset the Noritz tankless water heater by disengaging it for 30 seconds.

Error Code 92 And 93

Problem: Neutralizer has reached the end of its lifespan.

  • Replace the neutralizer and reset the burner timer according to the instructions of the Noritz hot water heater manual.


As you can see, numerous things can go wrong with a Nortiz tankless water heater.
These issues don’t occur frequently but need immediate attention when they do.
You can fix many of them yourself if you feel confident enough.
However, if you are unsure, we recommend hiring expert services for Noritz tankless water heater troubleshooting.
We are optimistic you enjoyed our thorough guide on how to reset the Noritz tankless water heater.
If you have any questions or concerns, leave us a comment.

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