High
F13 on Glow-worm Flexicom sx

Your boiler has lost communication with the temperature sensor on your hot water cylinder, meaning it cannot tell how hot your water is.

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

Tank NTC fault

From this model's manual
Verified against the Glow Worm Flexicom 18sx installation & service manual, page 46.
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 can no longer receive an electrical signal from the temperature probe attached to your hot water tank. The most common cause is a failure of the sensor's internal components or a loose connection in the wiring that links the cylinder to the boiler's main control board.

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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