BoilerFaultCodesYour boiler has detected that a temperature sensor is not fitted correctly to its pipe, preventing it from reading the water temperature safely.
Book a Gas Safe engineer within 24–48 hours. Your boiler may be unsafe or could break down completely if left.
Technical description: Temperature sensor incorrectly installed
What causes this fault?
This fault occurs when the boiler's control board detects that a temperature sensor is not providing a logical reading, usually because it has physically detached from the pipe it is meant to monitor. The most common reason is a broken or loose retaining clip, or the sensor being displaced during recent maintenance, preventing it from accurately tracking the water temperature. Without this direct contact, the boiler cannot safely regulate heat and will stop running to prevent overheating.
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 F.85 — 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.