BoilerFaultCodesYour boiler has lost connection with its outdoor temperature thermometer, so it does not know how hard it needs to work to heat your home.
This is a minor fault. Keep an eye on it and mention it at your next annual boiler service. Reset the boiler and see if it clears.
Technical description: Outdoor sensor not detected.
What causes this fault?
This fault occurs when the boiler's control board can no longer communicate with the external weather sensor mounted on the outside of your property. The most common reasons are physical damage to the sensor housing by the elements or a break in the low-voltage wiring that connects the sensor to the boiler. Without this signal, the boiler cannot automatically adjust its temperature based on the weather outside.
This fault is often discovered during the first cold snap of autumn or winter when the boiler attempts to use the outdoor sensor to ramp up the heating for the first time in months.
Engineer required
This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.
Find a Gas Safe engineer
Search the official register for a qualified engineer in your area.
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A boiler cover plan would cover faults like CC — no call-out fees, no surprises.
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