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ErrBase

Noritz Water Heater Ignition Failure: Causes When No Error Code is Shown

Quick Answer

When a Noritz tankless water heater fails to ignite with no error code on the display, the most common culprits are a gas supply that has been turned off or interrupted, a dirty flame rod that cannot form an ionization signal, a spark gap on the igniter that has widened from wear, and gas supply pressure too low to support combustion.

When a Noritz tankless water heater fails to ignite with no error code on the display, the most common culprits are a gas supply that has been turned off or interrupted, a dirty flame rod that cannot form an ionization signal, a spark gap on the igniter that has widened from wear, and gas supply pressure too low to support combustion. This differs from Code 11 (where the unit attempted ignition and the controller logged the failure) because here the unit may not be getting far enough in the startup sequence to register a fault. The absence of a code can mean the flow sensor is not triggering the sequence at all, or the fault clears before the controller can log it.

NoritzWaterheaterSeverity: highDifficulty: intermediate76% DIY Success
Time to Fix
20–75 min
Difficulty
intermediate
Parts Cost
$12 – $35
Tools Needed
Phillips screwdriver, Fine steel wool (000 grade)
Wrong code?

Not seeing IGN-FAILURE on your display?

Select what your appliance is actually doing and we'll take you to the right guide.

error code on display
HUB
no ignition
11
flame lost during use
12
error code on display
RESET

What Does the IGN-FAILURE Code Mean?

Ignition failure symptom guide for when no error code is displayed. Covers gas supply, dirty flame rod, widened spark gap, and flow sensor as causes.

Most Likely Causes

Based on aggregated repair data, here is the probability breakdown for this error code:

Gas supply turned off or supply valve partially closed40%
Dirty or oxidized flame rod preventing ionization signal24%
Gas supply pressure too low to sustain ignition attempt22%
Spark igniter electrode gap too wide from wear14%

Symptoms You May Notice

  • No hot water with no error code on display
  • Unit appears in standby mode but does not fire
  • Clicking noise during demand but no flame
  • Unit fires occasionally but fails most of the time

Can you reset a Noritz waterheater to clear the IGN-FAILURE code?

Perform a soft reset before each ignition test: power off for 30 seconds, then power on. If ignition still fails after addressing gas supply and cleaning the flame rod, enter service mode to check for stored error codes that may point to a more specific fault.

Tools Required for Diagnosis

Phillips screwdriverFine steel wool (000 grade)Feeler gauge (spark gap check)Combustible gas detectorFlashlight

Diagnostic Checklist

Follow these steps in order. We start with the easiest external fixes before opening up the machine.

1

Confirm the gas supply valve at the unit is fully open: the

Confirm the gas supply valve at the unit is fully open: the handle should be parallel to the gas pipe. Also check the main gas shutoff and any isolation valves between the meter and the unit.

2

Verify active gas supply

3

Remove the front access panel and locate the flame rod

4

Inspect the spark igniter electrode gap

5

Enter service mode (hold Temp Up + Temp Down for 3 seconds) and

Replacement Parts

If your diagnostic testing proves the component has failed, you will need a replacement. We recommend OEM parts over aftermarket for water-handling components.

Part Name
Flame Rod (Flame Sensor)100001706 · $12–$25
Spark Igniter Assembly100001714 · $20–$35

Repair vs. Replace Calculator

Appliance Age (Years)7 Yrs
Labor Approach
Our Verdict
REPAIR
Estimated Cost: $24 (Parts) vs $1150 (New Machine)

Frequently Asked Questions

Why would a Noritz fail to ignite with no error code?
No error code can mean the unit is not getting far enough into the startup sequence to register a fault. If the flow sensor does not detect water flow, the ignition sequence never starts and there is nothing to log. It can also mean a transient fault (brief gas pressure drop) that resolved before the controller logged it. Check the flow sensor and gas supply before assuming a component has failed.
What is the correct spark gap on a Noritz igniter?
The spark electrode gap on most Noritz models is specified at 3 to 4 mm between the electrode tip and the ground strap. Use a feeler gauge to measure. Gaps above 5 mm produce a weaker spark that may not reliably ignite the gas-air mixture, especially when gas pressure is at the lower end of acceptable range.
How is this guide different from the Noritz Code 11 article?
The Code 11 article applies when the unit completes ignition attempts and the controller logs the failure as Code 11. This guide covers situations where the unit fails to ignite but no code is shown - meaning either the ignition sequence never started or the fault was too brief to register. The root causes overlap (flame rod, gas supply) but this guide adds flow sensor and startup sequence as factors.
Could a dirty air filter cause ignition failure on a Noritz?
Noritz tankless water heaters do not have a replaceable combustion air filter. The air intake is an open pipe with a terminal cap at the exterior wall. What can restrict combustion air is a blocked or partially obstructed intake vent cap at the exterior. Check the intake for debris, ice, or insect nests if all other ignition causes have been ruled out.
My Noritz ignites on the first try sometimes and fails on other tries. What causes intermittent ignition failure?
Intermittent ignition is a classic flame rod symptom. As the rod warms up from a successful run, the oxidation layer expands slightly and the ionization signal weakens on subsequent cold starts. Clean the flame rod and monitor if the intermittent failures stop. Gas pressure that fluctuates near the minimum threshold is the other common cause of intermittent behavior.

Related Noritz Waterheater Error Codes

Code: HUBNoritz Tankless Water Heater Error Codes: Complete NR and NRCP Series GuideCode: 11Noritz Code 11: No Ignition Fix for NR and NRCP SeriesCode: 12Noritz Code 12: Flame Failure During OperationCode: RESETHow to Reset a Noritz Tankless Water Heater and Clear Error Codes

Models Known to Experience IGN-FAILURE Errors

This repair applies to most Noritz waterheaters with this error code. Common model numbers include:

NRCP199-DV, NRCP111-DV, NR98-DV, NR66-DV, NR711

Last verified for technical accuracy on March 14, 2026