d High

Halstead d Fault Code

Also written as D — same fault.

The Halstead d fault code means: your boiler has failed an internal safety check because it cannot detect a flame, causing it to shut down for protection.. It appears on 1 Halstead model 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: Safety system failure/ No flame - Failure of internal self checking system
Typical repair cost £120-£350 (including labour)

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 d fault code

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

Source

Halstead d 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