Medium Lockout
E33 on Keston C36

Your boiler is having trouble measuring the temperature of your hot water because of a faulty internal sensor or a wiring issue.

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 short circuit – check connections to DHW sensor are in place

What causes this fault?

This fault occurs when the boiler's internal computer receives an incorrect electrical signal from the sensor that monitors your hot water temperature. The most common reason is that the sensor has suffered a physical failure or an electrical short, preventing the boiler from knowing how hot the water is. It can also be caused by loose or damaged wiring between the sensor and the main control board.

Engineer required

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

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Related fault codes

E34View →E35View →

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