E012 — Flame Loss
The flame signal is lost during operation — the burner ignites and fires, but the flame-rectification signal drops out partway through a call for heat and the control board shuts the unit down for safety. (This is different from E004, a false-flame code that trips when the board sees a flame signal while the gas valve is commanded off.)
- Keep using it?
- Limited use only
- DIY difficulty
- Moderate
- Verified against
- navieninc.com ↗
How to fix it
- Note whether the code appears immediately on ignition or partway through a long draw — this helps a technician narrow down gas-pressure vs. rod/venting causes.
- This is a combustion-safety fault — do not attempt to service the flame rod, burner ground, gas valve, or venting yourself.
- Contact a licensed gas appliance technician to inspect the flame rod and burner ground, verify gas pressure, check the venting, and test the PCB flame-sensing circuit.
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 buildup weakens the flame-rectification signal, which can drop out during firing.
- Poor ground at the burner assembly Flame rectification needs a solid earth ground — a corroded burner ground strap or loose chassis ground can cause the signal to be lost.
- Cracked flame rod ceramic insulator Lets the rectification current leak to ground intermittently, interrupting the signal mid-burn.
- Low or fluctuating gas pressure A pressure dip during firing can cause the flame to lift off the rod, breaking the signal.
- Recirculating flue gases An improperly terminated or restricted vent can pull combustion products back across the rod and destabilize the flame.
- Failed PCB flame-sensing circuit The flame amplifier circuit on the main board misreads a good signal as lost.
Related repair guides
More Navien tankless water heater codes
Frequently asked questions
What does the E012 code mean on a Navien tankless water heater?
The flame signal is lost during operation — the burner ignites and fires, but the flame-rectification signal drops out partway through a call for heat and the control board shuts the unit down for safety. (This is different from E004, a false-flame code that trips when the board sees a flame signal while the gas valve is commanded off.)
What causes the E012 code on a Navien tankless water heater?
Contaminated flame rod: Carbon, soot, or scale buildup weakens the flame-rectification signal, which can drop out during firing. Poor ground at the burner assembly: Flame rectification needs a solid earth ground — a corroded burner ground strap or loose chassis ground can cause the signal to be lost. Cracked flame rod ceramic insulator: Lets the rectification current leak to ground intermittently, interrupting the signal mid-burn.
Is it safe to keep using a Navien tankless water heater with a E012 error?
Limited use only. This is rated a serious-severity fault.
How do I fix E012 on a Navien tankless water heater?
Note whether the code appears immediately on ignition or partway through a long draw — this helps a technician narrow down gas-pressure vs. rod/venting causes. This is a combustion-safety fault — do not attempt to service the flame rod, burner ground, gas valve, or venting yourself. Contact a licensed gas appliance technician to inspect the flame rod and burner ground, verify gas pressure, check the venting, and test the PCB flame-sensing circuit.
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.