GREEN LED ON every 0.5-secs Low

Pro GREEN LED ON every 0.5-secs Fault Code

Also written as GREENLEDONEVERY05SECS — same fault.

The Pro GREEN LED ON every 0.5-secs fault code means: your boiler has paused because it has detected a minor temporary issue, likely linked to low water pressure or a small internal communication hiccup.. It appears on 1 Pro model in our database.

Monitor it

This is a minor fault. Keep an eye on it and mention it at your next annual boiler service. Reset the boiler and see if it clears.

Technical description: Temporary fault, e.g.: APS fault, low water pressure
Typical repair cost £0-120 (including labour)

DIY fix possible

Check the pressure gauge on the front of the boiler; if it is below 1.0 bar, top it up using the filling loop.Turn the boiler off and back on at the fused spur switch to clear the temporary error.Ensure all radiator valves are open and that there are no obvious leaks around the unit.

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Pro models that show the GREEN LED ON every 0.5-secs fault code

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

Source

Pro GREEN LED ON every 0.5-secs fault code information on this page is sourced and cross-checked against the official Pro service / installation manuals for each affected model.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 7 July 2026