BoilerFaultCodesHeatline Overheat Fault Code
Also written as OVERHEAT — same fault.
The Heatline Overheat fault code means: your boiler has switched itself off because the water inside it has become too hot, usually due to a lack of circulation or a blockage.. It appears on 2 Heatline models in our database.
Technical description: Overheat LED flashing. Temperature of the water flowing from the primary heat exchanger gets too hot and the switch opens, cutting off the electrical supply to the gas valve.
DIY fix possible
Check that your radiator valves are fully open to allow water to flow.Check the boiler pressure gauge and top up to 1.5 bar if it is too low.Reset the boiler using the control knob to see if the fault clears.
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Heatline models that show the Overheat fault code
Click a model for the full fault code list and model-specific repair notes.
Source
Heatline Overheat fault code information on this page is sourced and cross-checked against the official Heatline service / installation manuals for each affected model.
Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 7 July 2026