Navien fault codes, explained properly
Navien boilers use a three digit E code. They are less common in the North East than the big four, which means fewer engineers know them well. Here is what each one means.
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Reading a Navien fault code
Navien uses an E followed by three digits. They are a smaller presence in the North East than Worcester, Vaillant, Baxi and Ideal, which has a practical consequence worth knowing: fewer local engineers work on them regularly and parts are less likely to be on a van.
One Navien code is specific to this region in an interesting way. E517 is a mixing valve fault, and limescale is one of the causes. That matters more around Sunderland and Seaham, where the water is at the harder end of the Northumbrian range, than it does in Durham or Peterlee where it is soft.
The reset rule, and why it matters
Almost every fault code can be cleared with the reset button, and almost everyone presses it more than once. That is the single most expensive habit in domestic heating.
A lockout is the boiler protecting itself. Resetting it tells the appliance to try again. Once is reasonable, because genuine one off glitches do happen. Repeatedly resetting a boiler that is locking out on ignition means it is pumping gas into the combustion chamber and failing to light it, over and over. Repeatedly resetting an overheat lockout means asking it to fire again into a system that cannot carry the heat away. Both do real damage, and both turn a known price repair into a bigger one.
Reset once. If it locks out again, stop and get it looked at.
Navien codes in detail
E003, ignition failure
The boiler attempted ignition three times and never established a flame, so it has locked out.
Why it happens: Gas supply interrupted or restricted, a frozen condensate pipe, a worn electrode, or a failing ignition transformer.
What you can do: Check the gas is on and other gas appliances work. Thaw an external condensate pipe with warm water. Reset once.
What an engineer does: Tests working gas pressure at the appliance, checks the electrode and transformer, and reads the stored fault history rather than working from the current display alone.
E012, flame loss
A flame was established and then lost during operation, which is a different fault from failing to light at all.
Why it happens: Gas pressure dropping under load, a flue restriction, or a flame rod that has degraded.
What you can do: Reset once. If it recurs, stop and get it looked at properly.
What an engineer does: Carries out flue gas analysis at full rate and a working pressure test, which separates a supply issue from an appliance issue.
E016, overheat
The appliance has exceeded its safe operating temperature and shut down.
Why it happens: Heat is not being carried away. A circulation problem, a failed pump, sludge, or a partly blocked heat exchanger.
What you can do: Do not keep resetting. Check whether radiators heat at all and check the pressure.
What an engineer does: Measures the flow and return difference to establish whether water is moving, checks the system water, and assesses the heat exchanger. On a heavily sludged system the repair is a clean, not a part.
E030, exhaust thermistor fault
The sensor monitoring flue gas temperature is reading abnormally.
Why it happens: A failed sensor, a wiring fault, or genuinely high flue temperature caused by a scaled or blocked heat exchanger.
What you can do: Nothing safely.
What an engineer does: Tests the sensor against manufacturer figures, and importantly checks whether the flue temperature really is high, because that points at the heat exchanger rather than the sensor.
E046, pressure sensor fault
The water pressure sensor is giving readings the board does not accept.
Why it happens: A faulty sensor, air in the system, or genuinely low pressure that the gauge is not reflecting accurately.
What you can do: Check the pressure gauge. If it reads normally and the fault persists, the sensor is the likely culprit.
What an engineer does: Compares the sensor reading against an independent gauge, which immediately shows whether the sensor or the system is at fault.
E109, fan fault
The fan is not running correctly or the board is not receiving the expected speed signal.
Why it happens: A worn fan motor, wiring or connector fault, or a board issue.
What you can do: Nothing. The fan is inside a sealed chamber.
What an engineer does: Checks fan current and speed signal and inspects the flue for restriction before condemning the fan.
E517, mixing valve fault
The valve that blends hot water to the set temperature is not operating correctly.
Why it happens: A failed valve motor, a wiring fault, or limescale binding the valve. In moderately hard water areas such as Sunderland and Seaham, scale is a genuinely common cause.
What you can do: Note whether the hot water temperature is fluctuating, which helps.
What an engineer does: Tests the valve motor and travel, and checks for scale. If the area has harder water it is worth discussing a scale reducer on the incoming main at the same time.
What these repairs cost
Same approach as every other brand we work on. One fixed fee to attend and diagnose, one fixed price for the repair, agreed before anything is ordered.
The honest caveat on Navien is parts availability. Because they are less common here, a part occasionally has to be ordered rather than fitted from the van. Where that is the case we tell you the timescale at the visit rather than leaving you waiting on a call. Prices are published on our boiler repair cost page.
If E517 turns out to be scale related and you are in a harder water part of the region, it is worth reading what hard water does to a boiler around Sunderland before deciding what to do next.
Navien questions we get asked
Useful if you have one of the less common boilers in the region.
Do you actually work on Navien boilers? +
What does E517 mean and why does it matter where I live? +
E016 keeps coming back. Why? +
Is it worth keeping a Navien or switching brand? +
How many times can I reset it? +
Where do you cover? +
Other brands and what to do next
- Worcester Bosch fault codes
- Vaillant fault codes
- Baxi fault codes
- Ideal boiler fault codes
- Look any code up in the error code checker
- What a boiler repair actually costs
- Boiler repair across the North East
- Out of hours emergency cover
- Annual boiler servicing
Local pages: Sunderland, Durham, Washington, Chester le Street and Houghton le Spring.