High
PCB 38 HW light flashing on Ideal Classic FF

Your boiler's hot water sensor is struggling to communicate with the main control board, meaning the system cannot accurately monitor the water temperature.

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

This indicates an 'open circuit' or 'short circuit' HW sensor or lead.

From this model's manual
Verified against the Response Ff80 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.

What causes this fault?

This fault occurs when the boiler's internal computer loses track of the hot water temperature because the sensor has failed or its wiring has become damaged. The most common reason is that the sensor has physically degraded over time or a loose connection has developed, preventing the boiler from safely heating your water.

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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