Slow Flashing (2Hz) High

Glow-worm Slow Flashing (2Hz) Fault Code

Also written as SLOWFLASHING2HZ — same fault.

The Glow-worm Slow Flashing (2Hz) fault code means: your boiler has failed to ignite and has locked itself out for safety, meaning you currently have no heating or hot water.. 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: Slow Flashing (2Hz)

What causes the Glow-worm Slow Flashing (2Hz) fault?

This fault occurs when the boiler attempts to start up but fails to detect a flame after several attempts. The most common reasons are a worn-out ignition spark that can no longer light the gas or a faulty gas valve that isn't letting fuel into the burner.

This issue is more frequent during the first cold snap of winter when components that have been idle over summer are suddenly put under heavy strain.

Typical repair cost £120-350 (including labour)

DIY fix possible

Check that your gas supply is turned on at the meterTurn the control knob to 'Reset' for 5 seconds and then back to the desired settingIf you have a prepay meter, check that you have enough credit

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Glow-worm models that show the Slow Flashing (2Hz) fault code

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

Source

Glow-worm Slow Flashing (2Hz) 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