BoilerFaultCodes.com
F12 Medium Lockout

Your boiler's hot water sensor has stopped working, meaning the system cannot accurately monitor the temperature of the water coming out of your taps.

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: DHW sensor error

What causes this fault?

This fault occurs when the boiler's internal sensor for hot water has failed or is producing an erratic electrical signal. The most common reason is that the sensor's internal thermistor has degraded over time or the wiring connecting it to the main control board has become loose or corroded.

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

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Protect yourself from future repair bills

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