d.33 High

Heatline d.33 Fault Code

Also written as D33 — same fault.

The Heatline d.33 fault code means: your boiler has detected that the internal fan responsible for safely venting fumes is not spinning at the correct speed, so it has stopped working to prevent unsafe operation.. It appears on 7 Heatline 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: Speed setpoint of fan
Typical repair cost £180-350 (including labour)

Engineer required

This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.

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Heatline models that show the d.33 fault code

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

Source

Heatline d.33 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