How do I reset a Navien tankless water heater?

Turn the unit off at its power switch or the wall receptacle, wait about 30 seconds, then turn it back on. Some models also reset by pressing and holding the reset button on the front panel or controller. If the same code returns, stop resetting and have the unit diagnosed.

Where do I find the error code on a Navien?

It appears on the digital display on the front of the unit and mirrors to the remote controller and the NaviLink app if you have it. Write the code down before resetting — it's the fastest path to an accurate diagnosis.

Which Navien error codes are dangerous?

Treat E004 (false flame), E030 (exhaust overheat), and E515 (control board) as stop-and-call codes. If you ever smell gas or a carbon monoxide alarm sounds, leave the building and call PG&E or 911 first.

Why does my Navien keep throwing the same code?

A reset clears the display, not the cause. Recurring codes point to a persistent condition — gas pressure, scale, venting, or a failed sensor — that has to be corrected.

Can hard water cause Navien error codes?

Yes. Scale from Santa Clara Valley water is the leading cause of E016 and E030 overheat faults and contributes to sensor codes like E407. Annual descaling prevents most of them.

Do you charge to diagnose a Navien error code?

We explain our diagnostic policy on the phone before dispatching so there are no surprises, and we can often narrow the cause from a photo of your display before we come out.

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Navien Error Codes: What They Mean and How They're Fixed

Look up the code on your display, read what actually causes it in San Jose water and gas conditions, and find out whether it's safe to reset.

Call (408) 470-0191 Get a diagnosis

Open 24/7 · CSLB #1008381 · Navien service specialists

Technician reading a Navien tankless water heater error code on the control panel

Quick answer

Navien error codes are shown on the unit's front display or the remote controller. The most common in San Jose are E003 (ignition failure, usually gas pressure), E016 and E030 (overheating from hard-water scale), E110 (blocked intake or exhaust), and E438 (dirty air filter). A single power cycle is safe; if the code returns, the underlying fault is still present and the unit is protecting itself. Efficient Water Heaters, Inc. diagnoses every Navien code 24/7 at (408) 470-0191, CSLB #1008381.

Look up your code

E003Ignition FailureIgnition failure — the unit tried to fire but no flame was established.Safe to try one reset E004False Flame SignalFalse flame — the control board senses flame when the burner should be off.Stop and call E012Flame Loss During OperationFlame loss — the burner lit, then flame was lost during operation.Service soon E016Heat Exchanger OverheatOverheating — the outlet or heat exchanger temperature exceeded safe limits.Service soon E030Exhaust OverheatExhaust overheat — flue gas temperature is abnormally high.Stop and call E109Combustion Fan FaultAbnormal fan operation — the combustion fan is not running at commanded speed.Service soon E110Air Pressure / Exhaust BlockageAir pressure / exhaust blockage — combustion air or exhaust flow is obstructed.Safe to try one reset E351Recirculation Sensor FaultWater-related sensor fault on the recirculation/return side.Service soon E407Water Temperature Sensor AbnormalityWater sensor abnormality — the unit reads an out-of-range water temperature signal.Service soon E438Clogged Air Intake FilterClogged air filter — the intake filter needs cleaning or replacement.Safe to try one reset E515Control Board (PCB) FaultAbnormal operation of the control board (PCB).Stop and call E782Communication ErrorCommunication error between the unit and a control, remote, or cascaded unit.Service soon

How to reset a Navien tankless water heater

1
Check the display and write the code down
Note the exact error code shown on the Navien control panel — E003, E016, E030, and E110 all point to different systems. The code tells a specialist which test to run first.
2
Confirm gas, water, and power are on
Verify the gas valve at the unit is open, the service switch is on, the breaker has not tripped, and no other gas appliance in the house is out. A closed valve after unrelated work is a common cause.
3
Press and hold the reset button
Hold the power/reset button on the front panel for about three seconds until the display clears, then release. Some models require turning the unit off and back on at the service switch instead.
4
Run a hot tap and watch the burner
Open a hot fixture for two minutes. The unit should fire, hold a steady outlet temperature, and show no code. Cycling between warm and hot usually means scale on the heat exchanger.
5
If the code returns, stop and call a specialist
A code that comes back within 24 hours is a real fault, not a glitch. Repeated resets on an ignition or exhaust fault can be unsafe — call (408) 470-0191 for same-day diagnostics in San Jose.

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