Navien Tankless Water Heater E012 — False Flame / Flame Loss
Navien Tankless Water Heater · Error code E012
What E012 Means
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.
Symptoms
- Unit shuts off mid-shower
- Brief hot water then cold
- E012 displayed
- Cycling on and off
Common Causes
Carbon, soot or scale on the rod gives a false or unstable signal.
Flame rectification needs a solid earth ground — corroded burner ground strap or loose chassis ground.
Allows leakage current to ground, mimicking a flame.
Pressure dip during firing causes flame to detach from the rod.
Improperly terminated or restricted vent pulls combustion products back across the rod.
Flame amplifier circuit on the main board reading incorrectly.
How to Fix It
- Power-cycle the unit and observe whether the code returns on the next call for heat.
- Remove and clean the flame rod with emery cloth; reseat firmly.
- Inspect ceramic insulator for hairline cracks — replace rod if cracked.
- Check and tighten the burner ground screw and chassis ground.
- Verify gas pressure stays in spec under full fire.
- Inspect intake and exhaust terminations for short-circuiting or blockage.
- If the code persists with a clean rod, good ground, and correct gas pressure, replace the PCB.
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
Verified against manufacturer documentation: navieninc.com
Always unplug an appliance before servicing it. This guide is for informational purposes and is not a substitute for a qualified technician.