Fast Flashing (8Hz) High

Glow-worm Fast Flashing (8Hz) Fault Code

Also written as FASTFLASHING8HZ — same fault.

The Glow-worm Fast Flashing (8Hz) fault code means: your boiler has detected an internal electrical error or a component failure during its startup sequence that is preventing it from firing up.. It appears on 4 Glow-worm models in our database.

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: Fast Flashing (8Hz)

What causes the Glow-worm Fast Flashing (8Hz) fault?

This fault occurs when the boiler's internal computer performs a safety check during startup and detects a conflict between the fan and the air pressure sensor. The most common reason is that the control board is receiving incorrect electrical signals, or a vital component has physically failed and is preventing the ignition sequence from completing.

Typical repair cost £180-450 (including labour)

Engineer required

This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.

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Glow-worm models that show the Fast Flashing (8Hz) fault code

Click a model for the full fault code list and model-specific repair notes.

Source

Glow-worm Fast Flashing (8Hz) 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