High
F.88 on Glow-worm 30cxi

Your boiler is struggling to keep a steady flame lit, which is causing it to shut down for safety.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed

Call an engineer soon

Book a Gas Safe engineer within 24 to 48 hours. Your boiler may be unsafe or could break down completely if left.

Technical description

Unstable flame (analogue input), underfloor heating contact or gas valve fault

Engineer required

This is a high severity fault. Stop using the boiler and call a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.

Find a Gas Safe engineer
Search the official register →

Related fault codes

F.28View →F.29View →

Related guides you might find useful

Pilot light keeps going out

Older boilers — thermocouple, draught, gas supply.

Read →

When to replace your boiler

7 signs repair isn't worth it anymore.

Read →

Is boiler cover worth it?

Break-even maths on monthly cover.

Read →