Noritz Water Heater Error 39: Meaning and How to Fix It

Noritz error code 39 typically indicates a false flame detection or combustion sensor issue that requires power resetting or professional inspection.

Table of Contents

What does error code 39 mean on a Noritz water heater?
What usually causes error code 39 to appear?
How do you perform a safe power reset?
What are the next steps if the reset fails?
Quick reference table
When should you stop and call a professional technician?
What information should you prepare before calling support?
How can you prevent error code 39 from returning?

What does error code 39 mean on a Noritz water heater?

Error code 39 typically indicates a false flame detection or combustion anomaly, meaning the control board senses a flame when the burner should be off.

This safety feature prevents the unit from operating under uncertain combustion conditions. Because error definitions can occasionally vary depending on your specific tankless model line or manufacture year, always confirm the code details in your owner manual.

The control board detects a flame signal when the gas valve is completely closed.
Moisture or condensation buildup inside the combustion chamber can interfere with the flame sensor reading.
A dirty or degraded flame rod can falsely report residual electrical current to the circuit board.
Improper grounding of the water heater unit can generate erratic signals resembling a live flame.
Internal electrical shorts or component wear on the main control board may trigger this alert.

What usually causes error code 39 to appear?

The most common causes include temporary electrical glitches, moisture accumulation around the burner, or a dirty flame rod sending false signals.

Tankless water heaters rely on precise electronic monitoring components to ensure safe combustion cycles. When soot, humidity, condensation, or loose wiring disrupts sensor communication, the system locks out to maintain home safety. Identifying whether the trigger is environmental moisture or a failing component dictates your next troubleshooting move.

High humidity or condensation droplets forming directly on or near the burner assembly components.
Carbon soot accumulation coating the flame rod surface and distorting electrical continuity readings.
Loose wiring harnesses connecting the flame sensor directly to the main circuit board.
Power surges or minor electrical fluctuations confusing the computerized logic on the control board.
A failing electronic control board unable to correctly interpret low-voltage sensor feedback signals.

How do you perform a safe power reset?

Perform a complete power reset by turning off the dedicated circuit breaker, waiting one minute, and restoring power to clear temporary electronic faults.

Always exercise extreme caution before interacting with any appliance electronics or wiring. Turn off the power supply completely at your home circuit breaker box to prevent electric shock hazards before removing the front metal cover to inspect internal components.

Locate the dedicated circuit breaker controlling your tankless water heater and switch it off.
Unplug the water heater power cord from the wall outlet if it is plugged in.
Wait at least sixty seconds to allow all internal capacitors to fully discharge completely.
Remove the outer metal casing screws carefully using a standard Phillips head screwdriver.
Inspect the interior wiring harnesses for any visible signs of moisture or loose connections.
Restore power at the circuit breaker to see if the error code clears successfully.

What are the next steps if the reset fails?

If a simple power reset fails to clear error code 39, you must inspect the flame rod and check for internal moisture issues.

Persistent error codes mean that the underlying electronic or environmental trigger remains active within the system. Carefully examine the burner compartment for any trapped water, condensation, or corrosion that might be bridging the sensor circuit and causing false readings.

Turn off the power breaker again before touching any internal sensors or wiring components.
Locate the flame sensor rod positioned inside the burner combustion chamber enclosure.
Unscrew the retaining fastener securing the flame sensor rod to the burner assembly.
Gently clean the metal rod tip using fine-grit sandpaper or a clean cloth.
Reinstall the clean flame sensor securely and tighten its mounting screw back down.
Turn the electrical power back on to test the water heater operation cycle.

Quick reference table

Match your specific appliance symptom with the most likely root cause and recommended corrective action to resolve the issue quickly.

Reviewing these common symptom correlations helps you determine whether a quick cleaning step will suffice or if professional intervention is required for safe operation of your home water heater system. Diagnosing exact patterns prevents unnecessary part replacements and ensures reliable hot water delivery.

Symptom	Likely cause / fix
Error 39 after heavy rain	Moisture in burner; dry components
Error code returns instantly	Faulty flame rod; clean or replace
Clicking sound with no ignition	Gas supply issue; check gas valve
Intermittent code during long showers	Overheating or condensation; inspect venting
Complete lockout after power surge	Control board glitch; perform hard reset

When should you stop and call a professional technician?

Stop troubleshooting and call a licensed technician immediately if you smell gas, detect a gas valve issue, or face internal component failure.

Gas appliances carry inherent safety risks involving open combustion and pressurized fuel lines. Never attempt complex gas valve repairs, closed-system adjustments, or electrical control board replacements on your own to avoid serious property damage, fire hazards, or personal injury.

You notice any suspicious odor of natural gas or propane near the appliance.
The error code immediately returns every single time you attempt a system reset.
Diagnostic steps require handling or testing gas supply valves and gas manifold components.
Internal water leaks are dripping directly onto electrical wiring or the control board.
You lack the specialized multimeter tools required to safely test low-voltage electrical circuits.

What information should you prepare before calling support?

Have your exact water heater model number, serial number, warranty details, and a summary of troubleshooting steps ready before contacting support.

Providing accurate documentation helps customer service representatives or service technicians diagnose your problem faster and more accurately. Having this appliance information organized saves valuable time during phone consultations and ensures you receive the correct factory-certified replacement parts.

Locate the metal rating label on the side of the unit for model and serial numbers.
Write down the exact error code history displayed on the digital control panel interface.
Note the specific date of purchase or professional installation to verify active warranty coverage.
List all troubleshooting steps and power resets you have already performed on the system.
Record any recent weather events or home electrical surges preceding the error code appearance.

How can you prevent error code 39 from returning?

Prevent future occurrences by scheduling annual maintenance, protecting outdoor units from extreme weather, and keeping internal filters clean.

Regular preventative care extends the operational lifespan of your tankless water heater and minimizes unexpected safety lockouts. Proactive maintenance ensures optimal combustion efficiency, prevents moisture buildup, and guarantees reliable hot water delivery throughout peak seasonal heating demands.

Schedule professional annual tune-ups to clean burners and check electronic sensor calibration.
Inspect outdoor venting terminals regularly to ensure they remain clear of leaves and debris.
Flush the heat exchanger periodically if you live in an area with hard water.
Protect outdoor-installed water heater models from driving rain and severe winter weather elements.
Check inlet water filters routinely to maintain proper water flow through the heat exchanger.

Frequently Asked Questions

Can I use my water heater while error code 39 is showing?

No, you should not attempt to use the water heater while error code 39 is active. The appliance has locked itself out to prevent unsafe combustion or false flame operations. Running water through the system during this state will only deliver unheated water until the underlying sensor fault is properly resolved.

What should I do if clearing the error code does not work?

If a standard power reset and flame rod cleaning fail to clear the error code, a component failure is likely present. You will need to contact a qualified service technician to test the control board and internal wiring. Continuing to force resets on a malfunctioning sensor can lead to permanent equipment damage.

Is error code 39 dangerous for my home?

Error code 39 itself is a built-in safety lockout designed to protect your home from potential combustion hazards. However, ignoring the root cause or tampering with gas components without professional training creates serious risks. Always respect gas safety guidelines and stop work immediately if you suspect a gas leak.

Does bad weather cause Noritz error code 39?

Severe weather, heavy driving rain, and high humidity can indeed trigger error code 39 on certain tankless models. Moisture can easily seep into the combustion chamber or affect exposed electrical terminals. Ensuring your outdoor exhaust vent and unit cover are properly sealed helps minimize weather-related electronic faults.

How much does it cost to repair a Noritz error code 39?

Repair costs for Noritz error code 39 vary depending on whether the issue is solved by cleaning or requires replacement parts. Simple cleaning or resetting is often covered under basic service calls. If a new control board or flame sensor is needed, expect typical professional repair ranges to vary by region and model.

Bottom Line

To resolve Noritz error code 39 safely, start by performing a complete power reset at your home circuit breaker. If the error persists after checking for moisture and cleaning the flame sensor, contact a licensed professional for assistance.

Sources

Noritz Owner’s Guide
Noritz Service Manual
Manufacturer Support Page
Plumbing and Heating Association