BoilerFaultCodesYour boiler's hot water sensor is struggling to communicate with the main control board, meaning the system cannot accurately monitor the temperature of your hot water.
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 fault. DHW sensor 10000 - 12000 ohms at room temperature. Wiring and connections to sensor.
What causes this fault?
This fault occurs when the sensor responsible for monitoring your hot water temperature fails to send a clear signal to the boiler's internal computer. The most common reason is that the sensor has physically degraded over time or a small leak has caused corrosion on the electrical connections. Without this data, the boiler stops heating water as a safety precaution to prevent it from becoming too hot.
Engineer required
This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.
Find a Gas Safe engineer
Search the official register for a qualified engineer in your area.
Gas Safe Register →Protect yourself from future repair bills
A boiler cover plan would cover faults like A4 — no call-out fees, no surprises.
Affiliate links — we may earn a commission at no extra cost to you.
Worcester Bosch Highflow 400 BF is discontinued — time for a new one?
Parts for discontinued models can be hard to find and expensive. A new A-rated boiler could save you money on both repairs and energy bills.
Affiliate links — we may earn a commission at no extra cost to you.