BoilerFaultCodes.com
LED 4 flash/second Medium Warning

Your boiler has detected an issue with the sensor that manages your hot water, meaning you will likely only have heating or very inconsistent water temperatures.

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 function failure / DHW sensor.

What causes this fault?

This fault occurs when the internal sensor responsible for measuring the temperature of your hot water fails or sends an incorrect signal to the main control board. The most common reason is that the sensor has physically degraded over time or developed a wiring fault, preventing the boiler from knowing how hot the water actually is. As a safety precaution, the boiler will often stop providing hot water to prevent accidental scalding.

Typical repair cost £90-160 (including labour)

Engineer required

This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.

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Protect yourself from future repair bills

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