BoilerFaultCodesYour boiler has shut down because a sensor has detected that the exhaust gases are getting too hot, which is a safety feature to prevent damage.
Book a Gas Safe engineer within 24–48 hours. Your boiler may be unsafe or could break down completely if left.
Technical description: Flue temperature sensor lockout
What causes this fault?
This fault occurs when the internal sensors detect that the waste gases leaving your boiler have reached an unsafely high temperature. The most common reasons are a buildup of scale or debris inside the main heat exchanger, which prevents heat from being transferred to your water, or a fault with the fan and sensor components themselves.
This issue often comes to light during the first cold spell of autumn when the boiler is suddenly required to run at maximum output for long periods.
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 F53 — no call-out fees, no surprises.
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Could it be time for a new boiler?
If repair costs are adding up, a new energy-efficient boiler could be the smarter long-term choice.
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