BoilerFaultCodes F.13 Medium Lockout
Your boiler's hot water sensor has developed an electrical fault, meaning the system cannot tell how hot your water is and has likely stopped heating it for safety.
Book a service
This fault should be looked at by a Gas Safe engineer within the next week or two. It may get worse if left.
Technical description: Short circuit: Domestic hot water cylinder temperature sensor
What causes this fault?
This fault occurs when the boiler's internal computer receives an abnormal electrical signal from the hot water sensor, indicating a short circuit. The most common reason is that the sensor has failed internally due to wear and tear, or the wiring connecting it to the main control board has become damaged or damp.
Typical repair cost £90-160 (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.
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A boiler cover plan would cover faults like F.13 — no call-out fees, no surprises.
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