BoilerFaultCodesYour boiler is not detecting that you have turned on a hot water tap, so it isn't starting the burner to heat the water.
Book a Gas Safe engineer within 24–48 hours. Your boiler may be unsafe or could break down completely if left.
Technical description: No red light (other lights function in other modes) - HW Mode
What causes this fault?
This fault occurs when the boiler fails to sense the flow of water when you open a hot water tap. It is usually caused by a rubber diaphragm that has perished or a mechanical internal switch that has become stuck, meaning the 'demand' for hot water never reaches the boiler's control board. Without this signal, the boiler remains idle because it doesn't know it needs to start the burner.
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 FAIL POINT E — no call-out fees, no surprises.
Affiliate links — we may earn a commission at no extra cost to you.
Worcester Bosch 24/28CDi II RSF 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.