BoilerFaultCodesYour boiler has detected that its temperature sensors are giving conflicting readings, which has caused it to stop working for safety.
Book a Gas Safe engineer within 24–48 hours. Your boiler may be unsafe or could break down completely if left.
Technical description: Permanent drift between flow sensor and return sensor
What causes this fault?
This fault occurs when the sensors monitoring the water leaving and returning to your boiler disagree on the temperature by a significant margin. The most common reason is that one of these sensors has become faulty or 'drifted' over time, sending incorrect data to the internal computer. In some cases, it can also be caused by a circulation issue or a failing control board misinterpreting the signals.
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 F28 — no call-out fees, no surprises.
Affiliate links — we may earn a commission at no extra cost to you.
Could it be time for a new boiler?
If repair costs are adding up, a new energy-efficient boiler could be the smarter long-term choice.
Affiliate links — we may earn a commission at no extra cost to you.