BoilerFaultCodesThe 6 most common faults
Your boiler has switched itself off because it has become too hot internally, usually due to a lack of water flow or a circulation problem.
Check if your radiator valves are open to allow water to flow.Check your boiler pressure gauge and top it up to 1.5 bar if it is too low.Press the reset button on the front of the boiler.
Your boiler is failing to light the gas or isn't staying lit, meaning you won't have any heating or hot water until it is reset or repaired.
Check that your gas meter is turned on and gas is reaching other appliances like a hob.If you have a pre-payment meter, ensure you have sufficient credit.Press the Reset button on the front of the boiler for five seconds.
Your boiler has sensed that there is not enough water flowing through the system, causing the pump to run without liquid.
Check the pressure gauge on the boiler or filling loop; it should be between 1 and 1.5 bar.If pressure is low, use the filling loop valves to top up the system water.Check that all radiator valves and isolation valves are fully open.Restart the boiler to clear the fault code.
Your boiler has stopped working because the fan isn't blowing air and fumes through the system as fast as it should.
Full guide for C1Your boiler has detected that a safety sensor is stuck, preventing the fan from starting up correctly to clear away waste gases.
Full guide for C4Your boiler's internal fan is working, but the safety system cannot detect enough air flowing through the flue to safely start the burner.
Full guide for C6on the British Gas RD 430i
Based on parts cited in our fault code database. Your engineer will confirm what's actually needed after diagnosis.
Call a Gas Safe engineer if…
- You can smell gas or see signs of a leak
- The British Gas shows an Emergency or High severity code
- The boiler keeps locking out after repeated resets
- You've tried the DIY checks and the fault hasn't cleared
- There's visible water leaking from the boiler
- The flame is yellow or orange instead of blue