Navien · Tankless Water Heater Serious

E012 — False Flame / Flame Loss

The control board sees a flame signal when the gas valve is commanded off, or loses the flame signal mid-burn. The unit shuts down for safety.

Keep using it?
Limited use only
DIY difficulty
Moderate
Verified against
navieninc.com ↗

How to fix it

  1. Power-cycle the unit and observe whether the code returns on the next call for heat.
  2. Remove and clean the flame rod with emery cloth; reseat firmly.
  3. Inspect ceramic insulator for hairline cracks — replace rod if cracked.
  4. Check and tighten the burner ground screw and chassis ground.
  5. Verify gas pressure stays in spec under full fire.
  6. Inspect intake and exhaust terminations for short-circuiting or blockage.
  7. If the code persists with a clean rod, good ground, and correct gas pressure, replace the PCB.

Why it happens

Typical signs: Unit shuts off mid-shower · Brief hot water then cold · E012 displayed · Cycling on and off

  • Contaminated flame rod Carbon, soot or scale on the rod gives a false or unstable signal.
  • Poor ground at the burner assembly Flame rectification needs a solid earth ground — corroded burner ground strap or loose chassis ground.
  • Cracked flame rod ceramic Allows leakage current to ground, mimicking a flame.
  • Low or fluctuating gas pressure Pressure dip during firing causes flame to detach from the rod.
  • Recirculation of flue gases Improperly terminated or restricted vent pulls combustion products back across the rod.
  • Failed PCB Flame amplifier circuit on the main board reading incorrectly.

Parts you may need

If diagnosis points to a failed part, these are the common replacements. As an Amazon Associate we earn from qualifying purchases.

More Navien tankless water heater codes

E003 E003 — Ignition Failure E003C E003C — Cascade Ignition Failure E016 E016 — Overheat / High-Limit Trip E027 Tankless E027 — Sensor Abnormality E030 E030 — Abnormal Exhaust Temperature (Flue Overheat) E046 E046 — Abnormality in Limit Control (Heat-Exchanger High-Limit)

All Navien codes → All tankless water heater codes →

Always unplug an appliance before servicing it. This guide is for informational purposes and is not a substitute for a qualified technician. Verified against manufacturer documentation: navieninc.com.