Low
C4 273 on Worcester Bosch 24 RSF

Your boiler has been running for a full 24 hours without a break and needs to turn off briefly to perform a safety self-test.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed

Monitor it

This is a minor fault. Keep an eye on it and mention it at your next annual boiler service. Reset the boiler and see if it clears.

Technical description

Airflow present during last 24 hour

DIY fix possible

Turn the boiler off using the main power switchWait for 30 secondsTurn the boiler back on to allow it to complete its startup safety checks

Find a Gas Safe engineer
Search the official register →

Related fault codes

C6View →

Related guides you might find useful

Is boiler cover worth it?

Break-even maths on monthly cover.

Read →

When to replace your boiler

7 signs repair isn't worth it anymore.

Read →

New boiler cost 2026

Realistic UK prices for a swap.

Read →