Noritz Tankless Error Code Troubleshooting

Noritz tankless water heaters have changed the game by offering endless hot water on demand. You no longer need to pay to keep a massive tank hot when you aren’t using it.

But even the best technology has a bad day. When your unit acts up, Noritz systems display specific error codes to help you diagnose the issue. These codes are incredibly helpful, but only if you speak the language.

We have broken down the most common Noritz error codes to help you get your hot water flowing again. This guide covers what the codes mean and how to fix them so you can potentially avoid a service call.

Where Do I Find the Error Code?

Noritz tankless water heaters feature a remote control for easy operation. This controller lets you set your ideal water temperature, toggle the power, and monitor the system.

When something malfunctions, the display on the remote control shows an error code. This number appears where you normally see the water temperature. If the display is blank or unresponsive, check your breaker panel or power supply before calling a pro.

Noritz Tankless Error Code Troubleshooting

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 system has an ignition failure.

The Solution

The unit is trying to fire up but cannot establish a flame.

1. Gas pressure: Verify the gas supply is open and the pressure matches the requirements in your owner’s manual.
2. Inspect for blockages: Check the intake and exhaust vents for obstructions.
3. Ignition rod: Ensure the ignition rod is clean and free of carbon buildup.
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 ⁽¹⁾, which forces the heater to work harder.

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 water level in the neutralizer is too high because it is not draining.

The Solution

This issue is specific to condensing models.

1. Examine the drain line: Ensure the drain line is not frozen, clogged, or pinched.
2. Check piping: Verify the condensate piping is sloped correctly to allow gravity flow.

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?

Noritz digital remotes remove the guesswork from troubleshooting. When the system malfunctions, the remote displays a specific error code in place of the temperature reading. Match this number to our guide or your owner’s manual to identify the exact failing component.

How Long Does a Noritz Tankless Water Heater Last?

Noritz tankless water heaters are built for longevity. While traditional tank heaters often fail after 10 to 12 years, a well-maintained Noritz tankless unit can last up to 20 years. Using a water softener and performing annual flushes will help you reach that 20-year mark.

Who Makes Noritz Water Heaters?

Noritz America produces these units for the US market. They are a subsidiary of Noritz Japan, a company founded in 1951. They are currently one of the leading manufacturers of tankless technology globally and focus specifically on high-efficiency water heating solutions.

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

Ignition failure (Error Code 11) is arguably the most common issue owners face. This occurs when the unit tries to light but fails due to low gas pressure or blocked airflow. Scale buildup (Error Code 16) is also very common in areas with hard water, as calcium deposits clog the heat exchanger over time.

Why Does My Noritz Tankless Water Heater Keep Shutting Off?

The most likely culprit is insufficient water flow. Noritz heaters require a minimum flow rate (usually 0.5 GPM) to activate the burner. If you are only running a trickle of water, the unit will shut down. Clogged aerators on your faucets or a dirty inlet filter screen can also restrict flow enough to cause random shut-offs.

How Do I Reset a Noritz Error Code?

For most error codes, you can reset the system by turning the power off at the remote control, waiting 30 seconds, and turning it back on. For a hard reset, unplug the unit from the wall outlet or flip the circuit breaker for one minute. Note that maintenance codes (like 92 or 05) often require a specific button sequence on the circuit board to clear.