BoilerFaultCodesYour boiler has lost its ability to accurately measure the temperature of the water coming back into the system, which is preventing it from heating up correctly.
Book a Gas Safe engineer within 24–48 hours. Your boiler may be unsafe or could break down completely if left.
Technical description: Return Thermistor Fault
What causes this fault?
This fault occurs when the sensor responsible for monitoring the temperature of the water returning to the boiler fails or provides an illogical reading. The most common reason is that the internal component has suffered an electrical failure or the wiring connecting it to the main control board has become loose or damaged.
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 L05 — 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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