Navien Water Heater Error E003 – Ignition Failure – Burner Never Lit
The heater sparked and opened its gas valve, but never saw a flame – often a closed valve or no propane.
Safety first · Consult a professional
An E003 lockout is protective: the gas valve closes when no flame is proven. If you notice a gas smell, don't try to relight or reset anything, don't use switches or phones inside, get out and call 911 or your gas utility from outdoors. If a CO alarm goes off, move everyone outside and call 911.
- Gas appliance: no DIY repairs. If you smell gas, leave the building, do not use switches and call your gas utility’s emergency line from outside.
- Carbon monoxide is odorless. Keep a CO alarm near fuel-burning appliances; if it sounds, get everyone outside and call 911.
At a glance
Severity: Moderate
- Meaning
- Ignition Failure – Burner Never Lit
- Typical repair cost
- $0–$1,500
- DIY difficulty
- Hard
E003 means the Navien ran its full ignition sequence – fan pre-purge, spark, gas valve open – yet the flame rod never confirmed a flame, so the control locked out. Navien's manuals (NPE tankless and NCB combi alike) give a single owner action for it: make sure the main gas supply valve is open. That points to the most common real-world triggers: a valve left closed after installation or service, an empty propane tank, or air in a new or recently opened gas line. When gas is definitely available and the code keeps coming back, the problem is low inlet gas pressure, a wrong gas-type setup, the igniter, the flame rod, the gas valve or the control board – all licensed gas-fitter or plumber territory.
How it looks on the display
Model families & display variants
| Model family | Shows | Note |
|---|---|---|
| NPE-A2 / NPE-S2 tankless water heaters | E003 | Manual: ignition failure – ensure the main gas supply valve is open. |
| NCB-E / NCB-H combi boilers | E003 | Same meaning; both space heating and hot water stop because the burner is shared. |
| Older NPE-A / NPE-S units and NaviLink app | E003 | Some people read or say it as "003" or "error 3"; it is the same ignition-failure code. |
Symptoms
- Cold water only; E003 appears within seconds of opening a hot tap
- You hear the fan and a clicking igniter, but never the soft whoosh of the burner
- Happens on the very first use after installation, a meter swap or a propane delivery
- Other gas appliances (range, dryer, furnace) also fail to light
- Propane models: tank gauge reads very low or the fault started on a very cold night
Possible causes
Ranked by how often each cause is behind this code (editorial estimate).
- Gas shut-off valve at the heater or at the meter closed or only partly open
- Propane tank empty or nearly empty, or the tank regulator iced up / shut off
- Air in the gas line after a new install, meter change or propane run-out
- Inlet gas pressure too low – supply line or meter too small for a high-input tankless heater
- Igniter or flame rod dirty, cracked, loose or with a poor connection
- Gas type mismatch – natural gas unit on propane (or vice versa) or conversion not completed
- Gas valve or main control board fault
Fix it step by step
Check for gas odor before anything else
Sniff around the heater and the gas piping. Any smell of gas means no resets and no further checks – follow the safety box instead.
Confirm the gas valve under the heater is fully open
The manual shut-off on the gas line feeding the Navien is usually a quarter-turn valve with a yellow handle. Handle in line with the pipe means open; across the pipe means closed. If it was closed or half-way, open it fully.
Tools: Flashlight
Cross-check another gas appliance
Try the range burner or see whether the furnace fires. If nothing gas-fired works, the problem is upstream – call your gas utility (natural gas) or propane supplier and don't touch the meter or regulator yourself.
Propane: read the tank gauge
If the gauge is near empty, order a delivery. After a tank has run completely dry, the supplier typically has to leak-test the system before turning gas back on, so tell them the tank ran out.
Think about recent gas work
A brand-new install, a meter replacement or a propane run-out often leaves air in the line. Purging it is the installer's or gas company's job – never loosen fittings to 'bleed' gas yourself.
One reset, then call a pro
Press the reset button once and open a hot tap. If E003 returns, a licensed plumber or gas fitter should measure the inlet pressure: Navien NPE units need 3.5–10.5 in. WC on natural gas and 8–13 in. WC on propane, checked with the heater at full fire.
How to reset E003
- Make sure there's no gas smell and the gas valve at the heater is fully open.
- Press the reset button on the front panel once (the Back button on NPE-A2/S2 models).
- Open a hot tap fully; within a few seconds you should hear the burner light and the display should show the outlet temperature rising.
- If E003 comes back, stop resetting – repeated ignition attempts on a gas problem don't fix anything.
Where the parts are
- 1Flue
- 2Fan
- 3Heat exchanger
- 4Ignition electrode
- 5Gas valve
- 6Circulation pump
- 7Expansion tank
- 8Pressure gauge
- 9Temperature sensor
Repair options & costs
| Repair | DIY? | Estimated cost |
|---|---|---|
| Open gas valve / propane refill (supplier leak check after a run-out) | No | $0–$150 |
| Service call: purge gas line and measure inlet pressure | No | $120–$250 |
| Clean or replace igniter and flame rod | No | $150–$350 |
| Replace gas valve | No | $350–$700 |
| Upsize gas supply line or meter for the tankless load | No | $400–$1,500 |
Rough US estimates; technician call-out fees vary by region. Not a quote.
When to call a technician
If the gas valve is open, other gas appliances work and one reset doesn't help, book a licensed plumber or gas fitter. Pressure testing, gas-type conversion, igniter and flame-rod service and gas valve replacement must be done by a qualified technician; a new installation that throws E003 from day one should go back to the installer.
Frequently asked questions
My new Navien shows E003 on the first day – what went wrong?
Most often the gas line still contains air, the valve wasn't fully opened, or the supply pipe is too small for the heater's input. All three are installation items, so call the installer back rather than paying someone else.
Why does my propane Navien show E003 only on very cold mornings?
Propane pressure falls as the tank gets cold and low, and a regulator can ice up. A large tankless burner then can't get enough gas to light. Keep the tank above a quarter full in winter and have the supplier check the regulator.
What's the difference between E003 and E012?
E003 means the flame never appeared at startup. E012 means the burner lit fine and then lost its flame while running, which shifts the suspects toward gas pressure under load, grounding and the intake filter.
Is it safe to keep pressing reset until it lights?
No. Each attempt sends gas into the burner; if it isn't lighting there's a reason. One reset after checking the valve is reasonable, after that it's a job for a professional.
Sources
- Official Navien user documentation and support pages (facts only; wording is our own)
- Methodology: How We Build Code Pages · Data Sources We Use · Editorial Policy