BoilerFaultCodes F16 Low Warning
Your boiler has lost its connection to the outside temperature sensor, meaning it cannot automatically adjust its performance based on the weather.
Monitor it
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: Outside sensor open circuit
What causes this fault?
This fault occurs when the electrical path between the boiler's control board and the external sensor is broken. The most common reasons are a loose connection at the terminal block, damaged external wiring caused by weathering, or a complete failure of the sensor’s internal components.
Typical repair cost £70-140 (including labour)
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.
Gas Safe Register →Protect yourself from future repair bills
A boiler cover plan would cover faults like F16 — no call-out fees, no surprises.
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