BoilerFaultCodesProtherm neon 1 not lit Fault Code
Also written as NEON1NOTLIT — same fault.
The Protherm neon 1 not lit fault code means: your boiler is not receiving any electrical power, which could be due to a tripped switch or an internal fuse failure.. It appears on 1 Protherm model in our database.
Technical description: Fault with mains supply or PCB fuse
DIY fix possible
Check if your home's main fuse box has tripped a circuit breaker.Ensure the boiler's isolation switch (fused spur) is turned on.Try replacing the 3-amp fuse in the external boiler switch if you are comfortable doing so.
Find a Gas Safe engineer
Search the official register for a qualified engineer in your area.
Gas Safe Register →Avoid the next call-out bill
A cover plan would handle faults like neon 1 not lit: no call-out fees, no surprise bills.
Affiliate links. We may earn a commission at no extra cost to you.
Protherm models that show the neon 1 not lit fault code
Click a model for the full fault code list and model-specific repair notes.
Source
Protherm neon 1 not lit fault code information on this page is sourced and cross-checked against the official Protherm service / installation manuals for each affected model.
Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 7 July 2026