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Every Noritz Tankless Error Code and How to Clear It

By Peter Gray
Updated
That blinking number on the remote is your heater asking for help.

A Noritz tankless heater fires only when you open a tap, so there is no full tank sitting hot all day waiting for you. That runs quietly for years, right up until the remote stops showing a temperature and shows a bare number instead.

That number is a Noritz error code, and it names the exact part that stopped cooperating. Code 11 means the burner never lit. Code 16 means the water ran too hot. Code 29 means condensate is backing up inside a condensing model.

Below is every common Noritz code, what it is actually reporting, and the fixes in the order worth trying. It also flags the handful of codes you should hand straight to a licensed technician rather than chase yourself.

Key Takeaways

  • A Noritz error code replaces the temperature reading on the remote control display, so a remote showing 11 or 16 is reporting a fault, not a setting.
  • Code 11 is an ignition failure, and a carbon-fouled ignition rod is its most common cause.
  • Cut the power and close the gas before opening a Noritz unit for any maintenance.
  • Maintenance codes such as 05, 92, and 93 will not clear with a power cycle until the service itself is done.

In This Article

Where Do I Find the Error Code?

Your Noritz error code shows on the remote control display, in the spot where the water temperature normally sits. That same controller is where you set the target temperature and switch the unit on and off, so the code takes over a screen you already read every day.

The number replaces the temperature rather than sitting beside it, which is how you tell a fault from a setting. Write the code down before you power cycle anything, because a reset clears the display and you lose the one piece of information that tells you which part failed. If the display is blank or unresponsive instead, check your breaker panel or power supply before calling a pro.

What Does Each Noritz Error Code Mean?

The codes below are grouped by what the heater was trying to do when it stopped: light the burner, read a water temperature, move combustion air, or drain condensate. Find your number, read what it is reporting, then work the fixes in the order listed.

BE SAFE

Troubleshooting error codes on a tankless water heater involves working around electricity and gas. For safety reasons, make sure you turn off the power and gas before carrying out any maintenance. If you have any uncertainty about what you are doing, call a professional technician instead.

Error Code 05

What It Is Telling You

  • This is a specific service warning.

The Solution

This automatic reminder indicates that your unit needs service from a qualified Noritz technician.

  1. Do not reset immediately: Do not try to clear this code before the service is complete.
  2. Schedule maintenance: Ignoring this warning could lead to a total system failure.

Error Code 10

What It Is Telling You

  • The power dropped, or gas combustion continued after you turned the unit off.

The Solution

Debris or grease can sometimes sustain a flame even after the gas valve closes.

  1. Check the burner: Look for foreign materials like oil, grease, or dust in the burner assembly.
  2. Clean the burners: Carefully wipe away any debris you find.
  3. Reset the water heater: Turn the unit off, wait 30 seconds, and turn it back on.

Error Code 11

What It Is Telling You

  • The unit cannot light the burner. Ignition needs air, spark, and gas present at the same time, so a Code 11 means one of the three is missing.

The Solution

The heater senses a demand for hot water but fails to establish a flame. A carbon-fouled ignition rod is the most common cause, so start there (1). Work the list in order: the rod costs nothing to clean, while a gas or venting fault needs tools and, past a point, a technician.

  1. Ignition rod: Pull the ignition rod and wipe off any carbon buildup that blocks the spark. This clears the fault more often than anything else.
  2. Gas pressure: Verify the gas supply is open and the pressure matches the requirements in your owner’s manual.
  3. Inspect for blockages: Check the intake and exhaust vents for obstructions that starve the burner of air.
  4. Wiring: Check that the ignition wiring is tight and undamaged.

Error Code 12

What It Is Telling You

  • The flame is too weak to heat the water properly.

The Solution

This usually relates to airflow or dirty sensors.

  1. Airflow: Clear any blockages preventing fresh air from reaching the burner.
  2. Flame rod: Clean the flame sensor rod if it is dirty.
  3. Replace the rod: If cleaning fails, the part may be faulty.
  4. Adjust gas valve: A professional may need to adjust the airflow or gas valve to strengthen the flame.

Error Code 14

What It Is Telling You

  • The thermal fuse has failed or blown.

The Solution

This is a safety device that trips to prevent overheating.

  1. Thermal fuse: If the fuse is burnt out, replace it with a new one.
  2. Check airflow: Ensure obstructions aren’t causing the unit to overheat.
  3. Heat exchanger: Inspect the exchanger for sediment clogging.
  4. Flush the unit: Use a kit to flush the heat exchanger according to manufacturer instructions.

Error Code 16

What It Is Telling You

  • The water temperature spiked too high.

The Solution

This is commonly caused by scale buildup from hard water (2), which insulates the heat exchanger so the burner drives the outlet temperature past its limit. Noritz recommends descaling on a schedule rather than waiting for Code 16 to force the issue: every 1 to 3 years in normal water, and every 12 months where the supply is hard (3).

  1. Descale the unit: Flush the system using white vinegar or a descaling solution.
  2. Reset the code: After descaling, disconnect the power for 20 seconds and reconnect it.

Error Code 20

What It Is Telling You

  • The high limit switch has tripped.

The Solution

This switch acts as a thermostat cut-off for safety.

  1. Inspect the switch: Check the high limit switch for physical damage and replace it if needed.
  2. Descale: Scale buildup can trigger this heat-related error, so descale your unit.

Error Code 29

What It Is Telling You

  • The neutralizer is not draining, so condensate is backing up inside a condensing model.

The Solution

This code only appears on high-efficiency condensing units, which drain acidic condensate through a neutralizer. When the neutralizer or its drain clogs, the heater shuts down to keep condensate from flooding the burner (4).

  1. Examine the drain line: Ensure the drain line is not frozen, clogged, or pinched. A line run outdoors can freeze and back up in cold weather.
  2. Check piping: Verify the condensate piping slopes downward for gravity flow. The heater has an internal trap, so do not add a second trap to the external line.
  3. Call a pro: Do not try to clear a drain line tied into the gas combustion system yourself. Have a licensed technician handle it.

Error Code 31

What It Is Telling You

  • The cold water thermistor (inlet sensor) has failed.

The Solution

The system cannot read the incoming water temperature.

  1. Replace the part: You need to install a new inlet thermistor.

Error Code 32

What It Is Telling You

  • The hot water thermistor (outlet sensor) has failed.

The Solution

The system cannot read the outgoing water temperature.

  1. Replace the part: Install a new outlet thermistor.

Error Code 33

What It Is Telling You

  • The heat exchanger thermistor has failed.

The Solution

This sensor monitors the temperature inside the core of the unit.

  1. Replace the part: Swap out the faulty heat exchanger thermistor.

Error Code 59

What It Is Telling You

  • The BTU input is too low, leading to combustion issues.

The Solution

This often happens if the gas supply is insufficient for the heater’s demands.

  1. Check gas pressure: Ensure the gas pressure settings match the owner’s manual for your specific location.
  2. Check vents: Inspect the combustion chamber intake for blockages.
  3. Clean components: Clean the burner chamber and fan motor to ensure smooth operation.

Error Code 61

What It Is Telling You

  • The fan motor has failed.

The Solution

The fan is critical for pushing exhaust out and pulling fresh air in.

  1. Check voltage: Test the voltage supplying the fan motor.
  2. Replace circuit board: If the voltage output is insufficient, the board may be bad.
  3. Replace fan motor: If the voltage is correct but the fan won’t spin, replace the motor.

Error Code 65

What It Is Telling You

  • The main flow control valve has malfunctioned.

The Solution

This valve regulates how much water moves through the system.

  1. Obstructions: Check vents and internal pipes for debris.
  2. Main control valve: Replace the flow control valve if it is stuck or broken.

Error Code 66

What It Is Telling You

  • The bypass control valve has failed.

The Solution

This valve helps mix water to achieve the precise output temperature.

  1. Inspect: Check the valve for blockages or scale buildup.
  2. Replace: Install a new bypass control valve if cleaning does not work.

Error Code 67

What It Is Telling You

  • There is an abnormality in the Air-Gas Mixer (AGM).

The Solution

This component ensures the perfect ratio of fuel to air.

  1. Power cycle: Turn the water heater off and back on.
  2. Replace: If the code returns immediately, you likely need a new air-gas mixer.

Error Code 70

What It Is Telling You

  • The computer circuit board has failed.

The Solution

This is the brain of the water heater.

  1. Replace board: You must install a new circuit board to fix this error.

Error Code 71

What It Is Telling You

  • There is an issue with the gas valve drive circuit.

The Solution

This indicates an electrical supply problem to the gas solenoid.

  1. Check voltage: Verify the unit is receiving clean, consistent power. This often happens with generators or after a power surge.
  2. Surge protection: Install a surge protector to prevent future occurrences.

Error Code 72

What It Is Telling You

  • The flame sensing device is malfunctioning.

The Solution

The unit thinks there is a flame when there shouldn’t be, or vice versa.

  1. Grounding: Verify the heater is properly grounded.
  2. Wiring check: Inspect the flame detection circuit and wires for damage.
  3. Replace parts: Replace the flame rod or circuit board if damaged.

Error Code 73

What It Is Telling You

  • The circuit board settings are incorrect.

The Solution

This usually happens if a jumper connection or dip switch was changed while the power was on.

  1. Power cycle: Unplug the heater completely for 30 seconds.
  2. Restart: Plug it back in and turn it on.
  3. Call a pro: If the code remains, the board may need reprogramming by a technician.

Error Code F76

What It Is Telling You

  • Communication error between multiple heaters linked by a quick-connect cord.

The Solution

This often occurs if you try to use more than one remote for the linked system.

  1. Remote check: Ensure only one remote control is connected to the bank of heaters.
  2. Reset: Unplug the units for 30 seconds and power them back on to sync the system.

Error Code 760

What It Is Telling You

  • There is a communication error with the remote control.

The Solution

The display cannot talk to the main unit.

  1. Wiring: Check the remote control wires for loose connections or damage.
  2. Conflicts: Ensure you don’t have multiple remotes connected improperly.
  3. Reset: Unplug the heater for 30 seconds and plug it back in.

Error Codes 90 and 91

What They Are Telling You

  • Abnormality in gas combustion (improper burning).

The Solution

The mix of air and fuel is off, creating inefficient or dangerous combustion.

  1. Blockages: Clear obstructions from the intake air filter and exhaust vents.
  2. Settings: Verify the gas and air mixture settings match the manual.
  3. Clean fan: Debris in the fan motor can slow it down, altering the air mix. Clean it out.

Error Code 92 and 93

What They Are Telling You

  • The condensate neutralizer is near the end of its life.

The Solution

The neutralizing media (rocks) inside the filter are depleted.

  1. Replace neutralizer: Install a new neutralizer kit.
  2. Reset timer: You must manually reset the internal burner timer via the circuit board. Consult your manual for the specific button combination.

Error Code 99

What It Is Telling You

  • The exhaust vent or air intake is completely blocked.

The Solution

The unit cannot breathe, so it shuts down immediately for safety.

  1. Inspect vents: Check the termination pipes outside your home. Look for bird nests, debris, or snow accumulation.
  2. Check connections: Ensure the venting pipes have not become disconnected or crushed.

FAQs

How Do You Troubleshoot a Noritz Water Heater?

Read the error code on the remote to troubleshoot a Noritz heater. The number that replaces the water temperature names the failing part, so match it to the list above or your owner’s manual before you touch anything. Then work that code’s fixes in order, because the cheap checks clear most faults: a fouled ignition rod, a blocked vent, a shutoff valve someone closed. Cut the power and close the gas before you open the unit, and stop at any step that touches the gas combustion system.

How Long Does a Noritz Tankless Water Heater Last?

A well-maintained tankless unit can last up to 20 years, according to Noritz, and the heat exchanger carries a 12-year warranty. That is roughly double the 10 to 12 years a standard tank heater gives you. Reaching that number depends almost entirely on descaling, every 1 to 3 years in normal water and every 12 months where the supply is hard. A water softener buys the heat exchanger more time in aggressive water, and it also keeps Code 16 from becoming an annual event.

Who Makes Noritz Water Heaters?

Noritz America makes and sells these units for the US market as a subsidiary of Noritz Japan. The parent company has built water heaters since the 1950s and builds both condensing and non-condensing gas tankless models. That matters when you read a code: Code 29 applies only to condensing models, and the 92 and 93 neutralizer codes track condensate hardware those units carry.

What Is the Most Common Problem With Noritz Tankless Water Heaters?

Ignition failure, shown as Error Code 11, is the most common Noritz problem. Ignition needs air, spark, and gas present at the same moment, so the code fires whenever any one of the three goes missing, whether that is a carbon-fouled ignition rod, a starved or closed gas supply, or a blocked intake. Scale buildup (Error Code 16) runs a close second in hard-water areas, where mineral deposits coat the heat exchanger and push the outlet temperature past its limit.

Why Does My Noritz Tankless Water Heater Keep Shutting Off?

A Noritz heater most often shuts off when water flow drops below the burner’s minimum, which according to Noritz is about 0.5 GPM on most models. Run only a trickle and the unit cannot sense enough demand to stay lit. Clogged faucet aerators, a partly closed shutoff, or a dirty inlet filter screen starve the flow sensor the same way, so clean those before you suspect the heater itself. A shutdown that arrives with a code on the display is a different problem, so read the number and work that code instead.

How Do I Reset a Noritz Error Code?

Reset most Noritz codes by switching the power off at the remote, waiting 30 seconds, and turning it back on. For a hard reset, unplug the unit or flip its breaker for one minute. Maintenance codes such as 05, 92, and 93 will not clear this way, because they track service intervals rather than faults, so they need a specific button sequence on the circuit board and usually the service itself completed first. If a code comes straight back the moment power returns, the fault is still live and no reset will hide it.

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About the Author

Peter Gray

Peter writes step-by-step guides that help homeowners fix leaks, replace faucets, and handle common plumbing repairs without calling someone in. Because he worked in the trade, he can also tell you which jobs are straightforward to do yourself and which ones are worth leaving to a licensed plumber.

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