High
0A18 on Alpha Pro Tec 24

Your boiler has detected an unusual and rapid change in water temperature, causing it to shut down for safety reasons to prevent overheating.

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

Flow and return sensor anomaly detected. Sudden temperature change detected on the flow or return sensor.

From this model's manual
Verified against the Alpha Pro Tec 24 installation & service manual, page 34.
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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