BoilerFaultCodesYour boiler's computer parts are not communicating correctly because they haven't been told which specific model of boiler they are installed in.
Book a Gas Safe engineer within 24–48 hours. Your boiler may be unsafe or could break down completely if left.
Technical description: When replacing both components [display and electronics], after being turned on, the appliance goes to fault and displays the error message “F70”.
What causes this fault?
This fault occurs when the boiler's internal computer boards lose their identity and no longer know which specific model they are controlling. It most commonly happens after a repair where new parts have been fitted but haven't been digitally linked to the boiler's unique settings. Without this specific configuration code, the system shuts down as a safety precaution because it doesn't know its own power rating or technical limits.
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 F70 — 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.