Error C1 264

Safety precautions:

1) If you smell gas or suspect a gas leak, leave the property immediately and call the gas emergency number. Do not operate electrical switches or the boiler. 2) If the boiler is showing an error and you can’t confirm it’s safe, switch the boiler off at the isolator and the room thermostat; do not attempt internal repairs. 3) Only perform non-invasive checks; any work on gas, flue, fan motor, wiring or PCB must be done by a Gas Safe registered engineer.

Initial homeowner checks (non-invasive):

1) Note the exact error: C1 264 and any other codes shown, and when it started (during heating, hot water, after a power cut, after service). 2) Try a single reset of the boiler using the reset button. Observe whether the boiler attempts to start and whether the code returns. Do not repeatedly reset more than 1–2 times if the fault recurs. 3) Check the external flue terminal (outside the building): look for obvious blockages such as leaves, debris, a bird’s nest, snow or ice. Do not insert tools down the flue. If you can safely remove light debris from the outside terminal, do so. 4) Check for frozen condensate pipe (common in cold weather) which can block discharge and trigger faults: if the external condensate pipe is frozen, thaw it with warm (not boiling) water or a warm cloth. 5) Check that the boiler has power (other lights, sockets) and that any fused spur or isolation switch to the boiler is on. Also check your house fuse box for tripped breakers.

Specific diagnostic steps you can safely try and what they indicate:

1) Reset once and listen: when the boiler tries to start, listen for the fan running for a few seconds. If you hear the fan spin then stop and the fault appears, that points to a fan stopping under load or a control/sensor cutting it out. If you hear no fan noise at all, that suggests a fan starting failure or power to the fan. 2) Look for additional codes or flue overheat messages (E9 etc.). A flue thermostat overheating or other sensor fault can also stop the fan and cause C1. 3) Note any recent works, storms, or animals around the flue which could explain a sudden blockage. 4) If the condensate pipe was frozen and thawing allowed the boiler to restart and run normally, the immediate issue may be resolved but an engineer should check for any damage and ensure correct installation/insulation of the condensate run.

When to call a professional and what to tell them:

1) Call a Gas Safe registered engineer if the fault persists after the simple, safe checks above or if you are uncomfortable performing the checks. Do not attempt to access or repair the fan, flue thermostat, wiring or PCB yourself. 2) Tell the engineer the exact model, the fault code C1 264, when it started, whether a reset temporarily cleared it, whether you found any external flue blockages or a frozen condensate pipe, and any power interruptions or recent work on the boiler or flue. 3) Likely professional diagnostics and fixes: the engineer will perform a controlled fan test and service menu checks, inspect fan wiring and connectors, check the flue and flue gas thermostat, test the fan motor and replace it if faulty, and inspect the control board if required. They will also check overall combustion safety and may replace sensors or the fan assembly as necessary.

Final notes:

1) Repeatedly resetting a boiler that is issuing safety lockouts is not advisable; stop and call a Gas Safe engineer if the fault reappears. 2) Do not attempt internal repairs on gas appliances; use a qualified engineer to protect safety and warranty. 3) Provide the engineer with the code C1 264 and the model details so they can bring the right parts and diagnostics equipment.