Navien E593 Fault Code: Causes, Fixes & Repair Costs
What does the Navien E593 fault code mean?
The E593 code on a Navien boiler signals that the control board has detected an abnormal condition with one or more of the physical buttons or keys on the front panel. In plain terms, the boiler's electronics are receiving an unexpected or continuous signal from a panel key — perhaps as though a button is stuck or is sending a constant input when it should not be. While this is not a gas or combustion safety fault, it will typically prevent the boiler from operating normally until the panel issue is resolved.
General guidance only — not a substitute for professional advice, and not certified by a Gas Safe engineer. Always have your specific appliance assessed by a qualified professional. Any gas work must be carried out by a Gas Safe registered engineer. If you smell gas or suspect carbon monoxide, leave the property and call the National Gas Emergency line on 0800 111 999.
Common causes
- Stuck or jammed panel button Common
A key on the front panel may be physically stuck in the pressed position, either due to mechanical wear, accidental impact, or a foreign object caught beneath it. The control board interprets a continuously held button as an error and raises E593 to flag the abnormal signal.
- Moisture or debris beneath the panel Common
Condensation, cleaning product residue, or dust can work its way behind the keypad membrane and cause a button to short or stick. This is particularly common in boiler cupboards where humidity levels can fluctuate, and often the fault appears intermittently before becoming persistent.
- Wear and tear on the keypad membrane Sometimes
Over years of use the rubber or plastic membrane that sits beneath the panel buttons can degrade, tear, or deform. A worn membrane may register a phantom keypress constantly, triggering E593 even when no button is being physically pressed.
- Front panel or display board failure Sometimes
The display board that drives the panel interface can fail electrically — for instance due to a voltage spike or component fatigue. If the panel is unresponsive, blank, or flickering alongside the E593 code, the panel assembly itself is likely at fault rather than an individual button.
- Main PCB fault Rare
In rarer cases the main printed circuit board misinterprets signals coming from a perfectly functional front panel. If a new panel is fitted and E593 persists, the underlying PCB may be sending or receiving corrupted data. Engineers can confirm this with electrical continuity and voltage testing using a multimeter.
How to fix it
- Visually inspect the front panel buttons DIY safe
Look carefully at each button on the front panel. Check whether any key appears sunken, crooked, or unable to spring back to its resting position. If a button looks stuck, try pressing it firmly once and releasing to see if it frees itself. Do not use tools or force that could damage the panel casing.
- Check for moisture or debris around the panel DIY safe
If there is visible condensation, dust, or residue around the panel buttons, gently wipe the surface with a dry, lint-free cloth. Do not spray any liquid directly onto the panel. Allow the area to dry fully before attempting a reset.
- Reset the boiler using the Back button DIY safe
Navien boilers can often be reset by pressing the Back button on the front panel. Hold it briefly, allow the unit to restart, and observe whether the E593 code clears. If the fault disappears and does not return, monitor the boiler over the next 24–48 hours. Limit manual resets to two or three attempts — repeated resets without a fix will not resolve an underlying hardware problem.
- Check your boiler warranty status DIY safe
Before calling an engineer, check whether your Navien boiler is still within its manufacturer warranty period and whether it has been serviced annually by a Gas Safe registered engineer. If both conditions are met, some or all of the repair cost may be covered, so contact Navien's official Technical Assistance Service (TAS) in the first instance.
- Contact a Gas Safe registered engineer for diagnosis Gas Safe engineer
If the E593 code persists after one or two resets, or if it keeps coming back, a Gas Safe registered engineer should attend to carry out proper electrical testing. The engineer will test wiring continuity and signal voltages between the panel and the main PCB using a multimeter to determine whether the fault lies with an individual button, the panel assembly, or the PCB itself. Do not attempt to open the boiler casing or disconnect any components yourself.
- Front panel replacement if diagnosed as faulty Gas Safe engineer
If the engineer confirms the panel keys or display board are at fault, the front panel assembly will need to be replaced. This is a job for a qualified engineer — it involves accessing internal wiring connections and ensuring the replacement panel communicates correctly with the main PCB. The engineer will test the boiler fully after fitting.
- PCB replacement if the panel tests serviceable Gas Safe engineer
Should the front panel check out as fully functional but E593 continues, the main PCB may be misinterpreting the panel signals. PCB replacement on a Navien boiler is a specialist task that must only be carried out by a qualified engineer, as incorrect fitting can cause further damage or create safety hazards.
Parts you may need
- Navien front panel keypad assembly · from £85
- Navien display board · from £130
- Navien main PCB · from £320
The exact spare depends on your boiler's GC number (on the data badge). Check this against the part before buying.
Typical repair cost
Expect to pay roughly £120–£400, depending on the underlying cause.
Frequently asked questions
Is E593 on a Navien boiler dangerous?
No — E593 is not a gas or combustion safety fault. It relates purely to the electronic interface between the front panel buttons and the control board. Your boiler may stop working normally while the fault is active, but there is no immediate risk of gas leak or carbon monoxide. That said, a boiler that cannot be operated properly should be fixed promptly, especially in cold weather.
Can I fix E593 myself without an engineer?
As a homeowner you can safely inspect the panel for stuck buttons, wipe away any visible moisture or debris, and attempt a reset using the Back button. However, if those steps do not clear the fault, the repair will require an engineer. Opening the boiler casing, disconnecting wiring, or replacing any internal components is not safe or legal without the appropriate Gas Safe registration.
How much does it typically cost to fix Navien E593 in the UK?
Most people with this fault pay between £120 and £400, covering the call-out, diagnosis, and either a front panel keypad or display board replacement. If the fault is traced to the main PCB rather than the panel itself, costs can rise significantly — PCB replacement on a Navien typically runs £450–£700 including parts and labour — but this is the less common outcome. Always ask your engineer for a written quote before authorising any work.
Will my Navien warranty cover the E593 repair?
Possibly, yes. Navien offers manufacturer warranties on their boilers, and if yours is still within the warranty period and has been serviced annually by a Gas Safe registered engineer, parts and labour for a front panel fault may be covered in full or in part. Contact Navien's official Technical Assistance Service (TAS) before booking an independent engineer, as using an unregistered or non-approved repairer could void the remaining warranty.