Navien Water Heater Error E012 – Causes & Fix
The burner lit, then lost its flame signal mid-cycle – think gas pressure, grounding or a dirty air filter.
Safety first · Consult a professional
Never try to work on the burner, gas valve or flame rod yourself. If there's a smell of gas, walk out without touching switches or phones and call 911 or the gas utility from outside; if a CO alarm sounds, get outside, call 911 and don't restart the heater until it has been inspected.
- 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
- Flame Loss – Burner Went Out While Running
- Typical repair cost
- $0–$1,500
- DIY difficulty
- Hard
E012 means the Navien lit and proved its flame, then lost that flame signal while it was heating. Navien's owner remedies are specific: clean the intake air filter, and make sure the electrical cord is properly grounded, because the flame rod works by passing a tiny current through the flame back to ground. In the field the classic pattern is a heater that runs fine for a sink but drops out when a shower and the dishwasher run together, which usually means gas pressure sags at full fire. Wind-driven exhaust recirculation, a coated flame rod and condensate problems are the other usual suspects, and diagnosing them needs a licensed technician with a manometer.
How it looks on the display
Model families & display variants
| Model family | Shows | Note |
|---|---|---|
| NPE-A2 / NPE-S2 tankless | E012 | Manual remedies: clean the intake air filter and ensure the power cord is properly grounded. |
| NCB-E / NCB-H combi boilers | E012 | Same definition; long space-heating runs at high fire can expose a marginal gas supply that short hot-water draws don't. |
| NaviLink app / front panel history | E012 | Repeated flame-loss events are counted in the installer information menu, which helps prove an intermittent fault. |
Symptoms
- Hot water turns cold partway through a shower, then E012 shows
- Drops out mainly when several fixtures, the furnace or the dryer run at the same time
- Worse on windy days or when snow piles up near the vent terminals
- Intermittent: runs for days, then several flame-loss lockouts in a row
- Heater is plugged into an adapter, extension cord or an old two-prong outlet
Possible causes
Ranked by how often each cause is behind this code (editorial estimate).
- Gas pressure sagging at full fire – undersized supply line or meter, several gas appliances firing at once, weak propane regulator
- Intake air filter dirty, starving the burner of air (Navien's first listed remedy)
- Poor ground or reversed polarity at the outlet, extension cord or adapter weakening the flame signal
- Flame rod coated, loose or cracked
- Exhaust being drawn back into the intake – terminals too close together, wind, snow drift
- Condensate backing up into the combustion area
- Intermittent gas valve or control board fault
Fix it step by step
Stop if anything smells wrong
Any gas odor or CO alarm ends the troubleshooting – follow the safety box. Otherwise continue.
Log when it drops out
Note what else was running: a second shower, the washer on hot, the gas dryer, the furnace, the range. If E012 only appears under combined demand, gas supply capacity becomes the prime suspect, which is very useful information for the technician.
Wash the intake air filter
With the unit switched off and unplugged, remove the front cover and pull the air filter (top left on NPE-A2/S2). Rinse and brush it clean, let it dry fully, then refit it and the cover.
Tools: Screwdriver, Soft brush
Check the power connection
The plug should go straight into a grounded three-prong receptacle – no cheater adapter and no extension cord. A plug-in outlet tester costs a few dollars and shows open ground or reversed hot/neutral; a wiring fault needs an electrician.
Look at the vent terminals outside
Check that intake and exhaust openings are clear of snow and debris and that exhaust can't easily blow back into the intake. Report terminals that sit very close together or in a wind-trap corner rather than moving anything yourself.
Tools: Flashlight
Reset once, then get it tested
Press reset and run a hot tap at full flow. If E012 recurs, a licensed plumber or gas fitter should measure inlet pressure with every gas appliance at high fire and check the flame rod; the installer menu also keeps a flame-loss counter that shows how often it has happened.
How to reset E012
- Make sure there is no gas smell and nothing is blocking the vent terminals.
- Press the reset button (Back button on NPE-A2/S2) once.
- Run a hot tap at full flow for a few minutes – the true test is sustained high demand, not a quick splash.
- If E012 returns, leave the error on the display for the technician and stop resetting.
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 |
|---|---|---|
| Clean the intake air filter (owner maintenance) | Yes | $0–$10 |
| Correct outlet grounding or polarity (electrician) | No | $120–$300 |
| Gas pressure diagnosis and regulator adjustment or replacement | No | $150–$350 |
| Replace flame rod (and gasket) | No | $150–$320 |
| Upsize gas line or meter so pressure holds at full fire | No | $400–$1,500 |
Rough US estimates; technician call-out fees vary by region. Not a quote.
When to call a technician
Book a licensed plumber or gas fitter when E012 keeps returning after the filter is clean and the heater is on a properly grounded outlet, and especially if it only happens under heavy combined demand. Measuring gas pressure at full fire, flame-rod service and vent corrections are not homeowner jobs.
Frequently asked questions
Why does E012 only happen when two showers are running?
At full input a tankless burner draws a lot of gas. If the line or meter is marginal, pressure collapses at high fire and the flame becomes unstable. A technician confirms this by measuring inlet pressure with all gas appliances firing.
Can a bad outlet really cause a flame-loss code?
Yes. The flame signal is a very small current that returns through ground, so an open ground, reversed polarity or an adapter plug can make a healthy flame look weak. Navien lists checking the ground as an owner step for E012.
Is E012 worse than E003?
Not necessarily, but it's harder to pin down because the burner does light. Intermittent flame loss is often a supply or venting issue rather than a failed part, so good notes on when it happens save diagnostic time.
Could wind really put out my water heater's flame?
Wind doesn't blow the flame out directly, but it can push exhaust back into the air intake when terminals are poorly placed. Burning its own exhaust makes the flame unstable, and the control reports flame loss.
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