E 91 Medium

Warmhaus E 91 Fault Code

Also written as E91 — same fault.

The Warmhaus E 91 fault code means: your boiler is temporarily limiting its performance because it has detected a reading that suggests the air mixture is not quite right, often triggered by flue conditions or pressure changes.. It appears on 1 Warmhaus model in our database.

Book a service

This fault should be looked at by a Gas Safe engineer within the next week or two. It may get worse if left.

Technical description: Air compensation active
Typical repair cost £120-250 (including labour)

Engineer required

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

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Warmhaus models that show the E 91 fault code

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

Source

Warmhaus E 91 fault code information on this page is sourced and cross-checked against the official Warmhaus service / installation manuals for each affected model.

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