F.88
FAULT CODE
Glow-worm
Unstable Flame / Gas Valve Fault (Energy Range)
High Severity
Engineer Required
On Glow-worm Energy boilers, F.88 indicates an unstable flame signal — possible underfloor heating contact issue or gas valve fault.
Step-by-Step Fix Guide
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Step 1 Engineer only
Call a Gas Safe engineer to check gas pressure, gas valve, and combustion settings
Gas Safe Reminder
Work on gas appliances must be carried out by a Gas Safe registered engineer. The steps above cover safe checks a homeowner can perform - any internal component replacement requires a qualified professional. If in doubt, always call an engineer.