Noritz Code 12: Flame Failure During Operation

Quick Answer

Noritz Code 12 means the water heater successfully ignited but the flame went out during operation. This distinguishes it from Code 11, where ignition never occurs.

Noritz Code 12 means the water heater successfully ignited but the flame went out during operation. This distinguishes it from Code 11, where ignition never occurs. The most common causes are gas pressure fluctuation during high-demand periods, a worn or contaminated flame rod that stops sensing the flame as it ages, water flow rate that drops below the minimum threshold mid-cycle, and vent restriction that starves combustion air. Code 12 that only happens with multiple fixtures running simultaneously usually points to gas pressure. Code 12 that happens randomly points to the flame rod.

NoritzWaterheaterSeverity: highDifficulty: intermediate74% DIY Success

Time to Fix

30–90 min

Difficulty

intermediate

Parts Cost

$12 – $80

Tools Needed

Phillips screwdriver, Multimeter

Wrong code?

Not seeing 12 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

error code on display

RESET

What Does the 12 Code Mean?

Flame established successfully but lost during operation. Check the flame rod and gas pressure before checking for vent issues or flow rate drops.

Most Likely Causes

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

Gas pressure dropping during high-demand periods40%

Worn or contaminated flame rod losing signal mid-cycle24%

Vent restriction reducing available combustion air22%

Water flow rate dropping below minimum threshold during use14%

Symptoms You May Notice

Code 12 on display after hot water use
Hot water that cuts out mid-shower
Unit runs for 30 to 60 seconds then shuts down
Code 12 only when multiple fixtures are in use

Can you reset a Noritz waterheater to clear the 12 code?

Press the power button off, wait 30 seconds, then press on. Code 12 will clear with a reset, but it will return if the root cause is not fixed. After fixing the identified issue, always reset before testing.

Tools Required for Diagnosis

Phillips screwdriverMultimeterManometer (gas pressure test)Fine steel wool (000 grade)Bucket and timer

Diagnostic Checklist

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

Note the pattern

Note the pattern: does Code 12 happen every use, randomly, or only when multiple fixtures run at once? Pattern identifies the most likely cause before testing any components.

Remove the front panel and access the flame rod

Test incoming gas pressure at the unit's test port with a

Run the unit at a single fully open hot water fixture

Inspect the exterior vent termination for partial blockage

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	OEM Number	Estimated Price
Flame Rod (Flame Sensor)100001706 · $12–$25	100001706	$12 – $25
Gas Pressure RegulatorN/A - utility-supplied or plumber-supplied · $30–$80	N/A - utility-supplied or plumber-supplied	$30 – $80

Verify part fitment for your Noritz model

Repair vs. Replace Calculator

Appliance Age (Years)7 Yrs

Labor Approach

Our Verdict

REPAIR

Estimated Cost: $46 (Parts) vs $1150 (New Machine)

Frequently Asked Questions

What is the difference between Noritz Code 11 and Code 12?

Code 11 means the unit never ignited during startup - no flame was ever detected during three attempts. Code 12 means the unit did ignite successfully, but the flame went out while the unit was running. They share the flame rod as a possible cause, but Code 12 also points to gas pressure instability and flow rate drops during operation.

Why does Noritz Code 12 only happen in the morning?

Morning peaks in utility gas demand reduce pressure in the supply line. If your gas meter or regulator is undersized relative to your home's total gas load, pressure can sag below the unit's minimum threshold, causing the flame to drop and trigger Code 12. This is most noticeable when gas demand across the neighborhood is highest.

Can I clean the flame rod to fix Code 12?

Yes, and it is the recommended first step. A flame rod with oxidation on its tip generates a weaker ionization signal. As the signal degrades during a heating cycle, the control board eventually loses confidence in the flame and shuts down with Code 12. Cleaning with steel wool takes 15 minutes and fixes the fault in roughly 30% of Code 12 cases.

My Noritz runs for exactly 2 minutes then shows Code 12. What is that?

A very consistent failure time often points to a thermal effect - a component that works when cold but fails once it heats up. The most common culprits with this pattern are the flame rod (oxidation behaves differently when hot) or a gas valve coil that loses conductivity as it warms. Have a technician check the flame rod signal voltage and gas valve coil resistance when the unit is warm.

Does Noritz Code 12 indicate a gas leak?

Code 12 itself does not indicate a gas leak. It means the flame went out. However, if the gas valve is stuck partially open and flame goes out, unburned gas could potentially accumulate. If you smell gas near the unit after a Code 12, do not reset - turn off the gas supply valve and ventilate the area before calling a technician.

Related Noritz Waterheater Error Codes

Code: HUBNoritz Tankless Water Heater Error Codes: Complete NR and NRCP Series Guide Code: 11Noritz Code 11: No Ignition Fix for NR and NRCP Series Code: RESETHow to Reset a Noritz Tankless Water Heater and Clear Error Codes

Models Known to Experience 12 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