BoilerFaultCodesThe 6 most common faults
Your boiler has shut itself down for safety because it has detected a significant electrical or mechanical issue with its internal components.
Why it happens: This fault occurs when the boiler's internal computer, the Printed Circuit Board, suffers a critical failure or receives abnormal electrical signals it cannot process. The most common reasons are a malfunctioning circuit board, a faulty ignition system that is confusing the controls, or a sudden electrical surge that has damaged the sensitive internal components.
Press and hold the 'Reset' button for five secondsWait for the indicator light to stop flashing or change to a steady lightIf the boiler refires, check that your thermostat is calling for heat
Your boiler has completely lost power and its display screen is blank, meaning it cannot operate or heat your home.
Why it happens: This fault occurs when the boiler's electrical circuit is broken, preventing power from reaching the internal computer. The most common reasons are a tripped fuse in your home's consumer unit, a blown fuse inside the boiler itself, or a total failure of the main printed circuit board. Essentially, the boiler is unable to 'wake up' because its electrical supply has been cut off.
Check if other appliances are working to rule out a general power cutCheck your home's main consumer unit (fuse box) to see if a circuit has trippedCheck the fused spur switch next to the boiler is turned on and the fuse inside hasn't blown
Your boiler has detected an internal computer error that prevents it from starting, meaning you currently have no heating or hot water.
Why it happens: This fault occurs when the boiler's internal computer experiences a critical electronic failure, preventing it from processing signals or managing components safely. The most common reasons are age-related wear on the circuit board's capacitors or an electrical surge that has damaged the delicate microchips. Because the control board can no longer communicate with the rest of the boiler, the system shuts down immediately as a safety precaution.
Full guide for Fast FlashingYour boiler's internal computer has developed a serious fault and can no longer control the heating or hot water safely.
Why it happens: This fault occurs when the boiler's central brain, the printed circuit board, fails its internal safety checks or loses communication with the sensors. The most common reason is electrical degradation of the components over time, or a loose connection in the wiring harness that prevents the system from operating safely.
Full guide for Fast flash / FlashingYour boiler has lost all electrical power, meaning it cannot provide heating or hot water until the connection is restored.
Check your home's main fuse box or consumer unit to see if a trip switch has turned off.Ensure the fused spur switch located near the boiler is turned on.Check if other electrical appliances on the same circuit are working.
Your boiler is not receiving electrical power or does not realise you are asking for heating or hot water.
Check if the boiler's power switch is turned onCheck your home's consumer unit (fuse box) to see if a circuit has trippedEnsure your thermostat is turned up and has working batteriesCheck if the external timer or programmer is set to 'On'
on the Worcester Bosch 28i RSF
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 Worcester Bosch 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