BoilerFaultCodesGlow-worm F.87 Fault Code
Also written as F87 — same fault.
The Glow-worm F.87 fault code means: your boiler is having trouble creating the spark needed to light the gas or recognizing that a flame has started.. It appears on 6 Glow-worm models in our database.
Technical description: Electrodes fault
What causes the Glow-worm F.87 fault?
This fault occurs when the boiler's internal computer tries to light the gas but the spark isn't strong enough or the sensors fail to detect a flame. The most common reasons are worn-out ignition pins that have corroded over time or a loose connection in the wiring that carries the electricity to create the spark.
Engineer required
This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.
Find a Gas Safe engineer
Search the official register for a qualified engineer in your area.
Gas Safe Register →Glow-worm models that show the F.87 fault code
Click a model for the full fault code list and model-specific repair notes.
Source
Glow-worm F.87 fault code information on this page is sourced and cross-checked against the official Glow-worm service / installation manuals for each affected model.
Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 27 April 2026