Emergency
Red LED (TTB) on Potterton Kingfisher MF 40-100

Your boiler has sensed a problem with the dangerous exhaust gases escaping, so it has automatically shut itself down to keep your home safe.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed

Act immediately

Turn off your boiler and stop using gas appliances. Call a Gas Safe engineer now. This fault can be dangerous if ignored.

What the manual says

Manufacturer manual

In the case of flue blockage this device will operate and the boiler will go to lockout (CF Models only).

From this model's manual
Verified against the Potterton Boiler Kingfisher Mf 40 100 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 emergency severity fault. Stop using the boiler and call a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.

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