C1 High

Worcester Bosch C1 Fault Code

The Worcester Bosch C1 fault code means: your boiler has stopped heating because the internal mechanism that pushes air through the system is not spinning fast enough to allow for safe combustion.. It appears on 24 Worcester Bosch models in our database.

Call an engineer soon

Book a Gas Safe engineer within 24 to 48 hours. Your boiler may be unsafe or could break down completely if left.

Technical description: Fan speed too low.

What causes the Worcester Bosch C1 fault?

This fault occurs when the boiler's control system detects that the internal fan isn't rotating fast enough to safely expel exhaust gases. It is usually caused by a build-up of dust on the fan blades, a failing motor, or a communication issue from the main control board. If the fan cannot reach the required speed, the boiler will shut down as a safety precaution to prevent fumes from staying inside the unit.

Typical repair cost £200-400 (including labour)

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 →
Boiler cover options

Avoid the next call-out bill

A cover plan would handle faults like C1: no call-out fees, no surprise bills.

Approved partner
Domestic Appliance Guard
Unlimited call-outs, 24/7 helpline, no price-hike promise
Get a quote →

Affiliate links. We may earn a commission at no extra cost to you.

Worcester Bosch models that show the C1 fault code

Click a model for the full fault code list and model-specific repair notes.

Source

Worcester Bosch C1 fault code information on this page is sourced and cross-checked against the official Worcester Bosch service / installation manuals for each affected model.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 7 July 2026