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ErrBase

Noritz Tankless Water Heater No Hot Water: Error 11, 12, 90 Diagnosis

Quick Answer

Noritz water heater not producing hot water: check the display for an error code first - each code points to a specific component. Igniter rod cracked or carbon-tracked (Error 11). For tankless units, annual descaling is critical in hard water areas - scale buildup is the most common cause of reduced output after 2-3 years.

Noritz tankless water heaters share similar error codes with Rinnai but have Noritz-specific causes. Error 11 = no ignition. On Noritz, the #1 cause is the igniter rod (not the flame rod - Noritz uses a separate igniter and flame sensor). The igniter generates a spark to light the gas. If the igniter is cracked or the ceramic insulator has carbon tracking, the spark cannot jump the gap. Clean the igniter tip and check for cracks. Error 12 = flame loss. Noritz is more sensitive to vent length than Rinnai - if the vent run exceeds the maximum for your model (check the installation manual), Error 12 appears during high-demand periods when combustion air is insufficient. Error 90 = combustion abnormality. This is Noritz-specific and indicates incomplete combustion from a dirty burner or restricted air supply. Clean the burner assembly (requires removing the front panel and burner cover).

NoritzWaterheaterSeverity: mediumDifficulty: intermediate75% DIY Success
Time to Fix
15–90 min
Difficulty
intermediate
Parts Cost
—
Tools Needed
Multimeter, Screwdriver

What Does the NO-HOT-WATER Code Mean?

Noritz no hot water: Error 11 = check igniter rod for cracks and carbon tracking (different from flame rod).

Most Likely Causes

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

Igniter rod cracked or carbon-tracked (Error 11)40%
Vent run exceeding maximum length (Error 12)24%
Burner dirty causing incomplete combustion (Error 90)14%
Gas supply restricted12%
Flame sensor oxidized10%

Symptoms You May Notice

  • Appliance exhibits no hot water behavior

Can you reset a Noritz waterheater to clear the NO-HOT-WATER code?

Unplug 60 seconds. Plug in and test.

Tools Required for Diagnosis

MultimeterScrewdriverFlashlight

Diagnostic Checklist

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

1

Follow the brand-specific diagnosis in the guide above.

Follow the brand-specific diagnosis in the guide above.

2

Check for error codes on display or LED patterns.

3

Run manufacturer diagnostic mode if available.

Frequently Asked Questions

How much does Noritz waterheater repair cost?
Most repairs $100-400 depending on the component.
Worth repairing or replacing?
If under 18 years and repair under 50% of replacement cost, repair.
DIY or professional?
Many fixes are DIY. Gas and sealed systems need professionals.

Last verified for technical accuracy on March 14, 2026