BoilerFaultCodesYour boiler has detected an issue with the sensor that confirms the flame is safely lit, causing the system to shut down 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: Ionization Probe & lead c/w Gasket & 2 screws
What causes this fault?
This fault occurs when the boiler's control system cannot detect a steady flame, causing it to shut down for safety. The most common reason is a buildup of carbon or debris on the ionization probe, which prevents it from sending a signal, or a failure in the electrical lead connecting the probe to the main board.
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 E85740 — no call-out fees, no surprises.
Affiliate links — we may earn a commission at no extra cost to you.
Potterton Powermax HE 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.