Noritz Tankless Error Code Troubleshooting

Note: This post may contain affiliate links. This means that at no cost to you, we may receive a small commission for made purchases.

Troubleshooting Noritz tankless water heater error codes isn’t as difficult as it may seem. Noritz, like any other tankless water heater manufacturer, uses a remote controller which can display various error codes on its LCD display to help with troubleshooting.

Need to Hire a Plumber?
Get a free estimate online from top local home service pros in your area.

Some Noritz problems can be fixed by a typical homeowner with a basic set of tools while others will require the services of a licensed professional. If you don’t feel 100% comfortable in attempting to fix the problem yourself, you can simply get a free, no-obligation quote from a local plumber to help you with your decision. Tankless water heater maintenance is different from traditional models so get professional help if you’re not sure.

NOTE: Below are some of the most common Noritz tankless water heater error codes you may see. You particular Noritz model may show codes different from what is below. In that case, please consult your owner's manual.

Have a different tankless water heater brand that needs troubleshooting?


Noritz Tankless Water Heater Error Codes

Error Code 05
What it Means: Service warning.

How to Fix: This is an automatic service reminder letting you know that it's time to call a licensed Noritz technician. Do not reset the error code prior to the service or the water heater may prematurely fail.

Error Code 10
What it Means: The power drops or gas combustion continues even after the unit is turned off.

How to Fix: Look for foreign materials (ie: oil or grease) on the burner which are still burning after gas combustion stops. To reset the code, turn the unit off and then on.

Error Code 11
What it Means: Ignition failure in your tankless water heater.

How to Fix: Check the gas pressure for correct values. Look for any obstructions in the vents as the fresh air supply might be being blocked. Remove any foreign materials from the ignition rod. Confirm there is no loose wiring in the ignition.

Error Code 12
What it Means: The tankless unit has a weak flame and the water is not being properly heated.

How to Fix: Confirm that there is enough airflow for proper gas combustion. Check that the flame rod/sensor is not covered by debris. Clean or replace if necessary.

Error Code 14
What it Means: The thermal fuse has failed.

How to Fix: Replace the thermal fuse. Confirm that the unit has no airflow restrictions and gas has proper combustion. Check water quality as hard water or sediment can cause the heat exchanger to get clogged. Flush the heat exchanger if necessary.

Error Code 16
What it Means: Water temperature is too high.

How to Fix: Since this is most often caused by hard water or scale buildup, a descaling procedure should be performed. To reset the code afterwards, unplug the water heater for 20 seconds and plug it back in.

Error Code 20
What it Means: High limit switch has been activated.

How to Fix: Check high limit switch and replace if necessary. Otherwise, perform the descaling procedure.

Error Code 29
What it Means: Water level in neutralizer is not properly draining making the water level exceed the correct level.

How to Fix: Make sure the condensate drain line is properly routed and unobstructed. Confirm condensate piping is the correct size and properly sloped.

Error Code 31
What it Means: Inlet (cold water) thermistor failure.

How to Fix: Replace inlet thermistor.

Error Code 32
What it Means: Outlet (hot water) thermistor failure.

How to Fix: Replace outlet thermistor.

Error Code 33
What it Means: Heat exchanger thermistor failure.

How to Fix: Replace the heat exchanger thermistor.

Error Code 45
What it Means: Water leak.

How to Fix: Close the water inlet valve and call for service if you notice a leak. If no visible leak, unplug the unit for 30 seconds to reset it and see if the code clears itself.

Error Code 59
What it Means: Low gas BTU input causing combustion problems.

How to Fix: Confirm correct gas pressure set and properly set for elevation where it's installed. Make sure enough airflow is getting to the combustion chamber by removing any noticable blockage of the vents. Clean fan motor and burner chamber.

Error Code 61
What it Means: Fan motor failure.

How to Fix: Check voltage coming to the fan motor. Replace fan motor or circuit board if necessary.

Error Code 65
What it Means: Main flow control valve failure.

How to Fix: Check for blockage and replace main flow control valve if necessary.

Error Code 66
What it Means: Bypass flow control valve failure.

How to Fix: Check for blockage and replace bypass flow control valve if necessary.

Error Code 67
What it Means: AGM (Air Gas Mixer) abnormality.

How to Fix: Turn the unit off then on. If the code reappears, the air gas mixer will likely need to be replaced.

Error Code 70
What it Means: Circuit board failure.

How to Fix: Replace circuit board.

Error Code 71
What it Means: Abnormality in gas valve drive circuit.

How to Fix: Confirm correct voltage. This error code is often seen when unit is connected to a generator or battery backup or if there is another type of voltage fluctuation. Install a power surge protector if necessary.

Error Code 72
What it Means: Flame rod detection abnormality.

How to Fix: Confirm that the water heater is properly grounded. Check for a damaged circuit board, flame detection circuit, or wires, and replace if necessary.

Error Code 73
What it Means: Improper circuit board setting.

How to Fix: Most likely a jumper connection or dip switch was changed on the circuit board while under power or the circuit board was improperly programmed. Unplug the unit for 30 seconds and plug back in. If the error code still shows up, call a licensed service tech.

Error Code 90 and 91
What it Means: Gas combustion abnormality.

How to Fix: Check airflow obstruction and improper gas burning. Confirm correct air/fuel mixture and gas pressure. Once fixed, reset the unit by unplugging for 30 seconds.

Error Code 92 and 93
What it Means: Neutralizer is at the end of its life cycle.

How to Fix: Replace neutralizer and reset burner timer.

Error Code 760
What it Means: Remote controller problem.

How to Fix: Check for loose wires and confirm only one remote is connected the the water heater. Unplug the unit for 30 seconds to reset.

Error Code 903
What it Means: Abnormal combustion.

Need to Hire a Plumber?
Get a free estimate online from top local home service pros in your area.

How to Fix: Confirm nothing is obstructing the intake or exhaust pipe.

Error Code 941 and 942
What it Means: Exhaust temperature is too high.

How to Fix: Check for and clear any air blockages and reset unit. If that doesn't work, call a licensed service tech.

Error Code F76
What it Means: Communication error between two tankless water heaters using Quick Connect cord.

How to Fix: Confirm that only one remote control is hooked up when multiple units are connected together. Unplug the unit for 30 seconds and plug back in to reset it.

Related Posts:


  1. I have an error code 67. What is it and is it fixable? I just put $3500 in repair of a 4 year old unit! Not happy with this unit. I had a rianni befor with no problems in 8 years.

  2. Regarding error code 67:
    After a power outage, the water heater indicated er.67.
    Power cycling the unit by unplugging the supply cord, the power button on the display panel, and the rocker switch behind the cover plate always returned to er.67.
    Finally, I tried: 1) Power off unit 2) Unplug AGM connector from control panel. 3) Plug AGM connector back into control panel. 4) Power unit back on.
    This cleared the error code and the unit is working again.

  3. My unit keeps blinking 903. It’s almost 3 years old and has shut off the last three days in a row blinking 903. Nothing more fun than a cold shower every morning because the water heater won’t stay on….

  4. I have Nortiz tank less water heater, I received error code 45 many times, but I do not know what is wrong with the tank. So, I want to know the exact problem with it.

    • ER45 is actually the code for a water leak somewhere in the unit. Check to make sure you’re not seeing any water drops within the unit. If you are, shut off the water inlet valve and contact a service technician. If you don’t see any water, you may want to reset the water heater to see if the code clears itself in case of a false positive.

  5. I have had the same model N-0751m Noritz unit for almost 10 years. I am on well water with some iron, I have a water softener filtering the water just before the heater. Also I had 8 children. About 4 years after use I started getting an error code 10 ( I pulled the fan out as far as I could and blew the dust off and re installed(little tricky but no problems for about 3 more years. Had to do the same thing again. Just this week the error code 10 came on. I blew the fan out again it worked but then it started giving me an error code 11 so I cleaned the ignition rods and I am getting an error code 90.
    I just pulled the power and waited 30 seconds.
    I Hoped would do the trick but it did not.

  6. What about code 941?
    Cold water and this code have happened 4 times in past two weeks… resetting the breaker works after 20 minutes but surely this unit should NOT be doing this after 10-11 months

  7. We’re getting error 91. Nothing about airflow has changed. Unit is 5-6 years old. Never an issue. Now this code has happened 4 times in a week. What gives? Any help appreciated.

  8. Hi with the Noritz combo boiler if I turn off the rocker switch part #28 will this clear the fault codes rather then unplugging the unit or pushing the power button on the control panel? I’ve had code 45 come up and there is no sign of water in the unit at all there was a leak on top of the unit where some water got in but the leak was fixed but the code 45
    Come up 1-2 time in 2 weeks and shuts the unit down so there’s no hot water

    • Hi I have noritz cb199-DV.
      I see outdoor reset icon…and no heating activated icon. So basically house is not getting heated. Does anyone know the solution to this ?

  9. I have a Noritz CB 180 DV. The DHW works. Whereas when there is demand for heating, it stops heating as the heating icon vanishes after about 3-4 minutes. The internal and external pumps keep going and there is no error code. Any suggestions?

  10. I have same problem with Joyce Widman. No codes but the burner is not firing on. I can hear the fan.

    Any idea on what is this problem

  11. Imm getting an error code F76 but I only have a single unit. I have had this unit for 12 years problem free! The error code says there is communication issues between two units. I only have one! ???????

  12. Have 2 units, 3 years old. They have faulted routinely since being installed, from communication errors to water leak from a defective part inside the unit. What are error codes 40 and 78? After 3 years of unpredictable hot water, we’re thinking of yanking them and installing another brand in their place.

  13. I’ve been getting an error code 60 but I can’t find any info on line. What does that mean? Besides no hot water. Any help appreciated. Thank you.

    • I had the same error code today. I couldn’t find the code in the manual, so I unplugged the unit, waited 30 seconds, and plugged in the power cord. The unit restarted and worked again. This is the second time in 2 years this has happened.

    • I get this code all of the time also. I think it means we need to descale the water heater because we have crappy water here. But we descake often and still get this code. Looking for an answer as well.

  14. I have a unique error…The unit stops producing hot water. When I look at the display the temperature display (115) and the priority/burner lights just flash indefinitely.
    If I unplug the unit and plug it back in again it powers up to the ‘OFF’ state and then I push the on/off button and it starts working. This can happen everyday for a week or not for weeks. I am puzzled


Leave a Comment