Medium Lockout
04E on Ravenheat HE 80/90 / 25-30s

Your boiler's hot water sensor has failed, which means the system cannot accurately heat water for your taps and showers.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed

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

Domestic hot water (DHW) sensor damaged

What causes this fault?

This fault occurs when the sensor responsible for monitoring the temperature of your tap water fails or sends an incorrect signal to the boiler's control board. The most common reason is the sensor’s internal components wearing out over time or the electrical wiring becoming loose or corroded due to heat exposure.

Engineer required

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

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Related fault codes

02EView →03EView →

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