AL74 High

Pro AL74 Fault Code

The Pro AL74 fault code means: your boiler has switched itself off because the water pressure is too low, causing the unit to get too hot.. It appears on 1 Pro 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: Over temperature due to low HO pressure
Typical repair cost £0-120 (including labour)

DIY fix possible

Locate the filling loop (the flexible silver hose) underneath your boiler.Slowly open the valves until the pressure gauge needle is between 1.0 and 1.5 bar.Close the valves completely and restart the boiler using the reset button.

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Pro models that show the AL74 fault code

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

Source

Pro AL74 fault code information on this page is sourced and cross-checked against the official Pro service / installation manuals for each affected model.

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