BoilerFaultCodesYour boiler has lost its connection to the external heating controls, meaning it cannot receive instructions on when to turn on or off.
Book a Gas Safe engineer within 24–48 hours. Your boiler may be unsafe or could break down completely if left.
Technical description: Break communication to FX sensor controls electrical connections need checking.
What causes this fault?
This fault occurs when the boiler's internal computer loses its digital handshake with your room thermostat or programmer. The most common reason is a hardware failure in the wireless receiver plugged into the boiler front, or degraded electrical wiring that physically links the controls to the main circuit 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 A8 — no call-out fees, no surprises.
Affiliate links — we may earn a commission at no extra cost to you.
Worcester Bosch CDi Classic 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.