Navien tankless water heater error E003: ignition failure

By Jason Dearmin · Last reviewed November 14, 2026 · How we check facts

What E003 means

Navien's NPN user manual, section 5.2 "Understanding Error Codes", lists E003 as Ignition failure. The heater called for heat, and the burner did not light.

Navien's two actions

1. Ensure that the main gas supply valve is open.
2. Ensure that the gas manifold and the fuel DIP switch setting match the supplied gas type.

Both are supply and setup checks. The second one matters most after a new installation or a gas conversion between natural gas and propane. Changing the DIP switch or gas manifold is an installer or technician task.

What a homeowner can safely do

• Confirm the gas valve at the water heater is open (handle in line with the pipe).
• If you use propane, check the tank level.
• Check that other gas appliances work. If they do not, the problem is the gas supply.
• Press Reset on the front panel once. Navien says that for minor problems, resetting the water heater may resolve the issue.

If E003 returns, Navien's manual directs further problems to an authorized technician or Navien Technical Support. For the NPN series the manual lists 1-800-519-8794; confirm the number for your model in your own manual.

Safe homeowner checks for Navien E003

1. Open the gas valveMake sure the main gas supply valve to the water heater is fully open.
2. Check propane supplyOn propane, confirm the tank has fuel.
3. Reset the unitPress the Reset button once. If E003 returns, contact an authorized technician.

Frequently asked questions

What causes E003 on a new Navien install?

Navien's manual points first to a closed gas valve and then to a mismatch between the gas manifold or fuel DIP switch setting and the gas actually supplied (natural gas versus propane).

Is E003 dangerous?

It is a safe shutdown when ignition fails. Treat a gas smell as an emergency: leave and call your gas utility.

Sources

• User's Information Manual: NPN Non-Condensing Water Heaters, section 5.2 Understanding Error Codes (Navien) Covers: Navien NPN-series non-condensing tankless water heaters (NPN-120E through NPN-199U). Condensing NPE/NCB models have their own manuals.

Safety note: this page is general information drawn from the sources above. Gas, combustion and line-voltage repairs belong to a licensed professional. Your own equipment's label and manual take priority over anything here. Read the full disclaimer.