BoilerFaultCodesYour boiler is receiving an unusual signal from the outdoor temperature sensor, likely due to a minor communication error or a faulty sensor outside 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: Time constant for calculating the adjusted outside temperature 21.3 hours
What causes this fault?
This fault occurs when the boiler receives inconsistent or 'out of range' data from the sensor mounted on the exterior of your property. The most common reason is a hardware failure within the sensor itself or moisture ingress into the sensor's casing that disrupts the electrical signal. It can also be caused by a loose connection or a break in the thin wiring that links the sensor to the boiler's internal control board.
This issue often surfaces during autumn or winter when heavy rain and frost are more likely to affect external wiring and sensor enclosures.
Engineer required
This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.
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A boiler cover plan would cover faults like 90:128 — no call-out fees, no surprises.
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