E127
Navien
Internal Configuration / Parameter Error
Boiler shows E127 and will not operate, often after service work
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Safety Warning
This repair may involve working with high voltage components or water connections. Always unplug the appliance before removing any panels.
If you are not confident in your ability to perform this repair safely, we strongly recommend contacting a professional technician.
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Possible Causes
Incorrect DIP switch settings, Corrupted control parameters, Incompatible PCB replacement, Misconfigured cascade settings
How to Fix / Troubleshooting
Safety first: Turn off power before adjusting DIP switches or control wiring.
- Step 1 – Verify DIP switches: Compare the DIP switch positions on the main PCB to the Navien installation manual for your exact model and application (space heating, DHW, cascade, etc.). Correct any mismatches.
- Step 2 – Reset parameters: Use the front control panel to perform a factory reset of control parameters if the manual allows. Re‑enter any custom settings afterward.
- Step 3 – Check cascade wiring: If multiple boilers are cascaded, verify the communication wiring and master/slave settings are correct.
- Step 4 – PCB compatibility: If the PCB was recently replaced, confirm the part number is correct for your model and firmware level.
If E127 persists, a Navien‑authorized technician may need to reprogram or replace the PCB.
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Repair Difficulty
Hard
4/5
Required Part
Main PCB (Control Board)
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