BoilerFaultCodesHalstead H. Fault Code
Also written as H — same fault.
The Halstead H. fault code means: your boiler has accidentally entered a testing mode used by engineers, which means it is currently operating at a very low power setting and may not provide enough heat or hot water.. It appears on 5 Halstead models in our database.
Technical description: SERVICE mode (flashing H.) - appliance runs at minimum CH output
Engineer required
This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.
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Halstead models that show the H. fault code
Click a model for the full fault code list and model-specific repair notes.
Source
Halstead H. fault code information on this page is sourced and cross-checked against the official Halstead service / installation manuals for each affected model.
Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 7 July 2026