Worcester Bosch C1 264 Fault Code: Causes, Fixes & Repair Costs
What does the Worcester Bosch C1 264 fault code mean?
The C1 264 fault code means the boiler's fan stopped running while the appliance was mid-cycle. Unlike fault codes that flag a fan failing to start, C1 264 is specifically triggered when the fan cuts out after operation has already begun — the PCB detects that the control signal or power supply to the fan has been lost mid-run. Without a working fan, combustion gases cannot be safely expelled through the flue, so the boiler shuts down immediately as a safety measure. The air pressure switch plays a key role here: it continuously monitors airflow and reports a sudden pressure drop to the PCB the moment the fan stops, triggering the lockout. Related fan codes you might see on Worcester Bosch boilers include C7 214 (fan not detected at startup), C6 215 (fan speed running too high), and C7 217 (erratic fan speed at startup) — but C1 264 is distinct in that the fan was working and then stopped.
General guidance only — not a substitute for professional advice. Any gas work must be carried out by a Gas Safe registered engineer. If you smell gas or suspect carbon monoxide, leave the property and call the National Gas Emergency line on 0800 111 999.
Common causes
- Faulty fan motor or failed fan unit Common
The fan motor itself may have burned out, seized, or developed an internal electrical fault. Because the fan was running at the start of the cycle before cutting out, a partial or intermittent motor failure is often the culprit. Fans are long-lived components, so outright failure without prior warning is less common, but age and wear do eventually take their toll.
- Wiring fault or loose electrical connection to the fan Common
A broken wire, corroded connector, or loose plug between the fan and the PCB can interrupt the control signal mid-cycle, causing the fan to drop out. Vibration over time can loosen connections, and this is a frequent cause of faults that appear intermittent or that a simple reset temporarily clears.
- Blocked flue or restricted airway Sometimes
A partial blockage in the flue outlet or air intake — caused by debris, bird nesting material, or ice in very cold weather — can overload the fan motor or cause it to stall. The air pressure switch then detects the loss of airflow and shuts the boiler down.
- Internal water leak causing electrical damage Sometimes
A leak anywhere inside the boiler can allow water to track along wiring, into connectors, or onto the fan itself. Water ingress introduces resistance or short-circuits connections, disrupting the signal between the fan, air pressure switch, and PCB. If you have noticed damp patches or corrosion inside the boiler casing, this possibility should be investigated.
- PCB fault Rare
If the PCB is no longer sending the correct control signal or power to the fan, the fan will stop even though the fan unit itself is in good condition. PCB faults are comparatively rare and are usually only confirmed once wiring and the fan have been ruled out.
How to fix it
- Check that your gas supply is working DIY safe
Make sure other gas appliances in your home — such as a hob or gas fire — are working normally. If you have no gas supply at all, contact your gas supplier before doing anything else. A interrupted gas supply will cause the boiler to shut down and could indirectly trigger fan-related fault codes.
- Inspect the flue terminal for visible blockages DIY safe
Go outside and look at where the flue exits the building. Check whether the outlet is visibly blocked by leaves, debris, ice, or nesting material. Do not attempt to reach into the flue or dismantle any part of it — this step is visual inspection only. If you can see an obvious external obstruction that can be safely removed without touching the flue pipe itself, do so. If the blockage is inside the flue or requires dismantling anything, leave it for an engineer.
- Reset the boiler once DIY safe
Press and hold the reset button (usually marked with a flame symbol or labelled 'Reset') for around three seconds. Allow the boiler to complete its startup sequence. A single reset is reasonable if the fault appeared out of nowhere. If the C1 264 code returns immediately or after a short run, do not keep resetting — repeated lockouts on the same fault indicate a real underlying problem that needs an engineer.
- Do not open the boiler casing or touch internal components Gas Safe engineer
Everything beyond this point — inspecting the fan, testing wiring, checking the air pressure switch, or examining the PCB — must be carried out by a Gas Safe registered engineer. Opening the boiler casing yourself is unsafe, will invalidate most warranties, and is not legally permitted for gas-related work.
- Have a Gas Safe engineer inspect the fan, wiring, and connections Gas Safe engineer
An engineer will remove the boiler casing safely, visually and electrically inspect the fan unit, and check all associated wiring and connectors for damage, corrosion, or loose terminals. They will measure the electrical supply to the fan to establish whether the fault lies with the fan itself, its wiring, or further upstream at the PCB.
- Replace the fan unit if it has failed Gas Safe engineer
If the fan motor has burned out or seized, a like-for-like replacement fan unit will be sourced and fitted. The engineer will ensure the new fan is correctly wired and that the air pressure switch is responding as expected once the fan is running. This is the most common resolution for a persistent C1 264.
- Investigate and repair any internal water leak Gas Safe engineer
If water damage to wiring or connections is found, the source of the leak must be identified and fixed before any electrical components are replaced or repaired. The engineer will assess the extent of any water damage and replace affected wiring, connectors, or components as required.
- Call a Gas Safe registered engineer if the fault persists or you are unsure Gas Safe engineer
If the reset did not clear the fault, or if the fault keeps returning, contact a Gas Safe registered engineer. You can find one at the official Gas Safe Register at gassaferegister.co.uk. Do not continue running the boiler while a fan fault is active — the boiler cannot safely expel flue gases without a functioning fan.
Parts you may need
- Boiler fan unit (Worcester Bosch compatible) · from £150
- Fan wiring loom / connector harness · from £25
- Air pressure switch · from £35
- PCB (if damaged beyond repair) · from £220
The exact spare depends on your boiler's GC number (on the data badge). Check this against the part before buying.
Typical repair cost
Expect to pay roughly £225–£375, depending on the underlying cause.
Frequently asked questions
Can I keep using my boiler while the C1 264 fault is showing?
No — you should not attempt to run the boiler with a C1 264 fault active. The fan is responsible for expelling combustion gases through the flue. If it has stopped, those gases have nowhere to go, which creates a genuine safety risk. The boiler's PCB has locked the boiler out for this reason. Leave it off until a Gas Safe engineer has identified and fixed the cause.
How much does it cost to fix a Worcester Bosch C1 264 fault in the UK?
For most households, the repair comes down to either a wiring fix or a fan replacement. A fan swap including parts and labour typically costs between £225 and £375 with an independent Gas Safe engineer. If the fault turns out to be a wiring connection issue only, the bill will usually be towards the lower end. In rare cases where PCB damage is involved — particularly if a water leak has been running for some time — costs can climb significantly higher, potentially £500 or more, though this is not the common scenario.
What is the difference between C1 264 and other Worcester Bosch fan fault codes?
Worcester Bosch boilers use several fan-related fault codes, and it helps to know which one you have. C1 264 means the fan stopped during an active cycle — it was running and then cut out. C7 214 means the fan was not detected at all when the boiler tried to start. C6 215 means the fan was running but at a speed higher than expected. C7 217 means the fan speed was erratic at startup. Each points to a slightly different cause, though all require a Gas Safe engineer to diagnose and repair.
Is it worth repairing a boiler showing C1 264, or should I replace it?
For a boiler under ten years old, a fan replacement is nearly always the more cost-effective option — a £225–£375 repair versus the cost of a new boiler installation, which typically starts around £2,000. For boilers over ten to twelve years old, or where additional faults or water damage are found during the inspection, it is worth asking your engineer for an honest assessment. If the total repair cost would exceed roughly half the price of a new boiler, replacement often makes better financial sense, and a modern A-rated condensing boiler will also reduce your heating bills.