High
F40 on Johnson Starley Quantec 24S

Your boiler has temporarily stopped working because the water pressure inside your heating system has dropped too low.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed

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.

What the manual says

Manufacturer manual

Central heating water pressure fault. The boiler restarts once the system pressure is built back up to the normal level.

From this model's manual
Verified against the Johnson Starley/Johnson Starley Quantec C System installation & service manual.
Plain-English guidance below. Severity, DIY steps, costs and parts are our interpretation to help you act, not text from the manual.

Engineer required

This is a high severity fault. Stop using the boiler and call a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.

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Related fault codes

F39View →F41View →

All 3 fault codes on the Quantec 24S

Seeing a different code? Every code this model can display, in one place.

E03F37

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