High
12 on Worcester Bosch Greenstar CDi Compact

Your boiler has detected an issue with the internal fan that pushes exhaust gases out, meaning it has safely shut itself down to prevent unsafe operation.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed

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

Locking Fan running too fast Defective fan or blocked air way. Fan running too slow No airflow after defined period of time Fan not running

Engineer required

This is a high severity fault. Stop using the boiler and call a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.

Find a Gas Safe engineer
Search the official register →

Related fault codes

12View →EAView →

Related guides you might find useful

Banging / kettling / whistling noise

Each noise points to a different fault.

Read →

When to replace your boiler

7 signs repair isn't worth it anymore.

Read →

Is boiler cover worth it?

Break-even maths on monthly cover.

Read →