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Worcester Bosch WR325 RSF Fault codes & diagnostics
67 fault codes with plain-English explanations, severity ratings, DIY guidance, and repair cost estimates.
Replaced by: Greenstar i Junior
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Severity at a glance
Each cell = one fault code. Hover to identify.All 67 documented codes
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10 Your boiler is failing to detect that water is circulating correctly, which is preventing it from firing up to provide your heating or hot water.
Your boiler is failing to detect that water is circulating correctly, which is preventing it from firing up to provide your heating or hot water.
Parts commonly replaced
- Flow sensor
- Diverter valve actuator
Related codes
12 Your boiler is failing to ignite or detect a flame, meaning your heating and hot water have stopped working.
Your boiler is failing to ignite or detect a flame, meaning your heating and hot water have stopped working.
Parts commonly replaced
- Ignition electrode
- Gas valve
- Flame rectification probe
Related codes
14 Your boiler has detected that it is getting too hot and has automatically switched itself off to prevent any damage or danger.
Your boiler has detected that it is getting too hot and has automatically switched itself off to prevent any damage or danger.
Parts commonly replaced
- Limit thermostat
- Pump
- Diverter valve
- Heat exchanger
Related codes
15 Your boiler is failing to detect the incoming electrical signal it needs to start or continue its heating cycle.
Your boiler is failing to detect the incoming electrical signal it needs to start or continue its heating cycle.
Parts commonly replaced
- Flow switch
- Printed Circuit Board (PCB)
- Wiring harness
Related codes
18 Your boiler is failing to light the flame needed to produce heat or hot water and has automatically shut down for your safety.
Your boiler is failing to light the flame needed to produce heat or hot water and has automatically shut down for your safety.
Parts commonly replaced
- Ignition electrode
- Ignition lead
- Printed Circuit Board (PCB)
Related codes
19 Your boiler is struggling to detect the water flow correctly, preventing it from switching on your heating or hot water safely.
Your boiler is struggling to detect the water flow correctly, preventing it from switching on your heating or hot water safely.
Parts commonly replaced
- Flow switch
- Microswitch
- Wiring harness
Related codes
28 Your boiler is struggling to communicate with your wall-mounted thermostat, which is currently preventing the heating from turning on.
Your boiler is struggling to communicate with your wall-mounted thermostat, which is currently preventing the heating from turning on.
Parts commonly replaced
- External thermostat
- Control module PCB
- Wiring harness
54 Your boiler has reached an unsafe temperature and has shut itself down to prevent damage to the internal components.
Your boiler has reached an unsafe temperature and has shut itself down to prevent damage to the internal components.
What to check first
- Check if any radiator valves have been accidentally closed and open them fully
- Ensure your system pressure is between 1 and 1.5 bar on the pressure gauge
- Gently bleed your radiators to remove any trapped air that might be blocking water flow
Parts commonly replaced
- Circulating pump
- Overheat thermostat
- Heat exchanger cleaning/replacement
Related codes
62 Your boiler is failing to detect that water is moving through the system, which is preventing it from safely firing up.
Your boiler is failing to detect that water is moving through the system, which is preventing it from safely firing up.
Parts commonly replaced
- Flow sensor
- Microswitch
- PCB
65 Your boiler has detected that it is running too hot and has automatically shut itself down to prevent damage.
Your boiler has detected that it is running too hot and has automatically shut itself down to prevent damage.
Parts commonly replaced
- Limit thermostat
- Pump
- Diverter valve
- Heat exchanger
Related codes
66C Your boiler has stopped working because it cannot confirm that the fan is safely pushing exhaust fumes out of the flue.
Your boiler has stopped working because it cannot confirm that the fan is safely pushing exhaust fumes out of the flue.
Parts commonly replaced
- Air pressure switch
- Fan assembly
- Venturi tube
Related codes
69 Your boiler is struggling to detect water moving through the system, which is preventing it from safely turning on your heating or hot water.
Your boiler is struggling to detect water moving through the system, which is preventing it from safely turning on your heating or hot water.
Parts commonly replaced
- Flow sensor
- Microswitch
- Diverter valve diaphragm
Related codes
112 Your boiler has lost the ability to accurately measure the temperature of the water returning to it, so it has stopped working as a safety precaution.
Your boiler has lost the ability to accurately measure the temperature of the water returning to it, so it has stopped working as a safety precaution.
Parts commonly replaced
- Return NTC sensor
- Wiring harness
114 Your boiler is failing to ignite the flame reliably, meaning it cannot produce heat or hot water.
Your boiler is failing to ignite the flame reliably, meaning it cannot produce heat or hot water.
Parts commonly replaced
- Ignition electrode
- Ignition lead
- Printed Circuit Board
Related codes
115 Your boiler is struggling to detect or control the flow of gas required to ignite the flame, meaning it cannot currently produce hot water or heating.
Your boiler is struggling to detect or control the flow of gas required to ignite the flame, meaning it cannot currently produce hot water or heating.
Parts commonly replaced
- Gas valve
- PCB
Related codes
116 Your boiler's water flow control mechanism is experiencing a communication error, which prevents it from properly managing the flow of hot water to your taps or radiators.
Your boiler's water flow control mechanism is experiencing a communication error, which prevents it from properly managing the flow of hot water to your taps or radiators.
Parts commonly replaced
- Diverter valve
- Actuator motor
- PCB
119 Your boiler is struggling to detect the flame needed to heat your water, which is causing it to shut down for safety reasons.
Your boiler is struggling to detect the flame needed to heat your water, which is causing it to shut down for safety reasons.
Parts commonly replaced
- Ignition electrode
- Flame rectification probe
- Ignition lead
Related codes
144 Your boiler has detected that the water temperature is rising too quickly while the burner is on, so it has stopped heating to prevent damage.
Your boiler has detected that the water temperature is rising too quickly while the burner is on, so it has stopped heating to prevent damage.
Parts commonly replaced
- NTC temperature sensor
- Central heating pump
- Heat exchanger
660 Your boiler has detected an electrical fault within its internal wiring or a control component, causing it to shut down for safety.
Your boiler has detected an electrical fault within its internal wiring or a control component, causing it to shut down for safety.
Parts commonly replaced
- Main Printed Circuit Board (PCB)
- Internal Wiring Harness
- External Controls Interface
Related codes
661 Your boiler is not receiving the correct electrical voltage needed to run, likely due to an issue with your home's power supply or a failing internal circuit board.
Your boiler is not receiving the correct electrical voltage needed to run, likely due to an issue with your home's power supply or a failing internal circuit board.
Parts commonly replaced
- Printed Circuit Board (PCB)
- Transformer
Related codes
662 Your boiler is failing to start up because the internal computer responsible for lighting the flame has encountered a fault.
Your boiler is failing to start up because the internal computer responsible for lighting the flame has encountered a fault.
Parts commonly replaced
- Printed Circuit Board (PCB)
- Ignition electrodes
- Wiring harness
Related codes
668 Your boiler has stopped working because the internal fan, which safely exhausts fumes, is not running correctly.
Your boiler has stopped working because the internal fan, which safely exhausts fumes, is not running correctly.
Parts commonly replaced
- Fan Assembly
- Air Pressure Switch
- Main Control Board
Related codes
669 Your boiler has stopped working because it cannot safely clear waste gases through the flue pipe.
Your boiler has stopped working because it cannot safely clear waste gases through the flue pipe.
Parts commonly replaced
- Fan assembly
- Air pressure switch
- Venturi tube
Related codes
A1 Your boiler has detected that a internal sensor responsible for measuring water temperature has stopped working correctly.
Your boiler has detected that a internal sensor responsible for measuring water temperature has stopped working correctly.
Parts commonly replaced
- NTC Thermistor
- Temperature Sensor
- Wiring Harness
Related codes
A2 Your boiler has detected an issue with the air supply or the way it releases exhaust gases, preventing it from firing up safely.
Your boiler has detected an issue with the air supply or the way it releases exhaust gases, preventing it from firing up safely.
Parts commonly replaced
- Fan
- Air pressure switch
- Flue seals
Related codes
A4 Your boiler has detected an issue with the air flow or the internal fan that clears away waste gases.
Your boiler has detected an issue with the air flow or the internal fan that clears away waste gases.
Parts commonly replaced
- Fan assembly
- Air pressure switch
- Flue venting components
Related codes
A5 Your boiler has detected an electrical communication problem with its internal control system which is preventing it from firing up.
Your boiler has detected an electrical communication problem with its internal control system which is preventing it from firing up.
Parts commonly replaced
- Main Printed Circuit Board (PCB)
- Wiring Harness
Related codes
A7 Your boiler is struggling to accurately measure the temperature of the water being heated for your taps and showers.
Your boiler is struggling to accurately measure the temperature of the water being heated for your taps and showers.
Parts commonly replaced
- Hot water NTC sensor
- Wiring harness
Related codes
A8 Your boiler has lost its internal connection between the main control board and the display panel, meaning it cannot communicate with itself properly.
Your boiler has lost its internal connection between the main control board and the display panel, meaning it cannot communicate with itself properly.
Parts commonly replaced
- Printed Circuit Board (PCB)
- Internal Ribbon Cable
- Display Interface
Related codes
A9 Your boiler is struggling to correctly flow water through the system, which is preventing it from heating up properly.
Your boiler is struggling to correctly flow water through the system, which is preventing it from heating up properly.
Parts commonly replaced
- Diverter Valve Diaphragm
- Diverter Valve Assembly
- Flow Sensor
Related codes
AC Your boiler has lost communication between its internal computer and a key electrical sensor or motor, meaning it cannot operate safely.
Your boiler has lost communication between its internal computer and a key electrical sensor or motor, meaning it cannot operate safely.
Parts commonly replaced
- Wiring harness
- Main PCB
- NTC Sensor
Related codes
Ad Your boiler is having trouble communicating with the sensor that monitors the temperature of your hot water cylinder.
Your boiler is having trouble communicating with the sensor that monitors the temperature of your hot water cylinder.
Parts commonly replaced
- Cylinder NTC sensor
- Wiring harness
Related codes
b1 Your boiler has lost its connection to its internal memory chip, meaning it no longer knows its specific configuration settings.
Your boiler has lost its connection to its internal memory chip, meaning it no longer knows its specific configuration settings.
Parts commonly replaced
- Code plug
- Printed Circuit Board (PCB)
Related codes
C0 Your boiler is having trouble controlling the flow of water through the system, which is likely affecting your hot water or heating performance.
Your boiler is having trouble controlling the flow of water through the system, which is likely affecting your hot water or heating performance.
Parts commonly replaced
- Flow regulation valve
- Motorised valve actuator
- Main PCB
Related codes
C1 Your boiler has stopped working because it cannot safely confirm that the fan is pushing exhaust fumes out of the flue.
Your boiler has stopped working because it cannot safely confirm that the fan is pushing exhaust fumes out of the flue.
Parts commonly replaced
- Air Pressure Switch
- Fan Assembly
- Venturi Tube
Related codes
C2 Your boiler has detected a problem with the way gas is being supplied or ignited at the burner, preventing it from heating your water.
Your boiler has detected a problem with the way gas is being supplied or ignited at the burner, preventing it from heating your water.
Parts commonly replaced
- Gas valve
- Burner assembly
- Ignition electrodes
Related codes
C4 Your boiler has detected an issue with the air pressure inside the system, which is stopping it from safely starting the burner.
Your boiler has detected an issue with the air pressure inside the system, which is stopping it from safely starting the burner.
Parts commonly replaced
- Air pressure switch
- Fan assembly
- Venturi tube
Related codes
C6 Your boiler's fan is not running at the correct speed or has stopped working entirely, which means the system cannot safely clear exhaust fumes and has shut down as a precaution.
Your boiler's fan is not running at the correct speed or has stopped working entirely, which means the system cannot safely clear exhaust fumes and has shut down as a precaution.
Parts commonly replaced
- Fan assembly
- Air pressure switch
- Main PCB
Related codes
d3 Your boiler has lost the signal from a required safety link or bridge, meaning it cannot safely start its ignition process.
Your boiler has lost the signal from a required safety link or bridge, meaning it cannot safely start its ignition process.
Parts commonly replaced
- Control board
- Wiring loom
- Link bridge (terminal block)
Related codes
E2 Your boiler has stopped working because it cannot correctly measure the temperature of the water leaving the unit.
Your boiler has stopped working because it cannot correctly measure the temperature of the water leaving the unit.
Parts commonly replaced
- Flow temperature sensor (NTC thermistor)
- Wiring harness connecting the sensor
Related codes
E4 Your boiler has detected a problem with how it controls the gas flow, meaning it cannot safely regulate the flame and has shut down as a precaution.
Your boiler has detected a problem with how it controls the gas flow, meaning it cannot safely regulate the flame and has shut down as a precaution.
Parts commonly replaced
- Gas Valve
- Modulator Coil
- Printed Circuit Board (PCB)
Related codes
E5 Your boiler is failing to detect a flame after it tries to ignite, causing it to shut down for safety.
Your boiler is failing to detect a flame after it tries to ignite, causing it to shut down for safety.
Parts commonly replaced
- Ionisation electrode
- Flame sensing lead
- Printed Circuit Board (PCB)
Related codes
E9 Your boiler has sensed it is getting too hot and has shut itself down as a safety precaution.
Your boiler has sensed it is getting too hot and has shut itself down as a safety precaution.
What to check first
- Check that your radiator valves are open and not turned off
- Ensure there is enough water pressure in the system by checking the pressure gauge
- Press the reset button on the front of the boiler control panel
Parts commonly replaced
- Overheat Thermostat (STB)
- Circulation Pump
- Temperature Sensor (NTC)
Related codes
E44 Your boiler has detected that there is too much water in the system combined with high temperatures, causing it to shut down for safety.
Your boiler has detected that there is too much water in the system combined with high temperatures, causing it to shut down for safety.
What to check first
- Check that the internal or external filling loop valves are fully closed.
- Bled water from a radiator bleed valve to reduce the system pressure.
- Monitor the pressure gauge to ensure it stays between 1.0 and 1.5 bar when cold.
- If pressure rises again without intervention, contact a Gas Safe engineer.
Parts commonly replaced
- Filling loop valve
- Expansion vessel
- Pressure relief valve
Related codes
EA Your boiler is failing to light the burner, meaning it cannot provide you with any hot water or heating.
Your boiler is failing to light the burner, meaning it cannot provide you with any hot water or heating.
Parts commonly replaced
- Ignition electrode
- Gas valve
- Ionisation probe
- PCB
EE2 Your boiler has detected that a temperature sensor is giving readings outside of its normal bounds, causing the system to shut down as a precaution.
Your boiler has detected that a temperature sensor is giving readings outside of its normal bounds, causing the system to shut down as a precaution.
Parts commonly replaced
- NTC Temperature Sensor
- Wiring Harness
- Main PCB
Related codes
EE4 Your boiler is struggling to spark or stay lit, which means your heating and hot water have stopped working.
Your boiler is struggling to spark or stay lit, which means your heating and hot water have stopped working.
Parts commonly replaced
- Ignition electrodes
- Lead set
- Ignition transformer
Related codes
EE5 Your boiler's gas valve is not opening or functioning correctly, preventing the system from producing heat or hot water.
Your boiler's gas valve is not opening or functioning correctly, preventing the system from producing heat or hot water.
Parts commonly replaced
- Gas valve
- Printed Circuit Board (PCB)
Related codes
EE6 Your boiler has detected an issue with the external valve system, preventing it from operating correctly and resulting in a total loss of heating and hot water.
Your boiler has detected an issue with the external valve system, preventing it from operating correctly and resulting in a total loss of heating and hot water.
Parts commonly replaced
- External zone valve
- Motorised valve head
- Wiring center
Related codes
EE9 Your boiler has detected a communication issue or a fault with one of its internal ignition electrodes, meaning it cannot safely light the burner.
Your boiler has detected a communication issue or a fault with one of its internal ignition electrodes, meaning it cannot safely light the burner.
Parts commonly replaced
- Ignition Electrode
- Flame Sensing Electrode
- Ignition Lead
- Control Board
Related codes
Explosive ignition Your boiler is struggling to light smoothly, causing it to build up a small amount of gas before igniting with a loud bang.
Your boiler is struggling to light smoothly, causing it to build up a small amount of gas before igniting with a loud bang.
Parts commonly replaced
- Pilot burner assembly
- Gas valve
- Ignition electrode
F0 Your boiler has detected a critical internal software or electronic processing failure and has stopped working as a safety precaution.
Your boiler has detected a critical internal software or electronic processing failure and has stopped working as a safety precaution.
Parts commonly replaced
- Printed Circuit Board (PCB)
Related codes
F7 Your boiler is detecting a flame inside its internal chamber when the burner should be completely turned off.
Your boiler is detecting a flame inside its internal chamber when the burner should be completely turned off.
Parts commonly replaced
- Gas valve
- Printed Circuit Board (PCB)
- Flame rectification electrode
Related codes
FA Your boiler has detected that the burner flame is still lit even after it has tried to turn the gas supply off, which indicates a serious safety malfunction.
Your boiler has detected that the burner flame is still lit even after it has tried to turn the gas supply off, which indicates a serious safety malfunction.
Parts commonly replaced
- Gas valve
- Printed Circuit Board (PCB)
Related codes
FC Your boiler's electronic control panel is not communicating with the main computer system, preventing the boiler from receiving instructions to heat your home.
Your boiler's electronic control panel is not communicating with the main computer system, preventing the boiler from receiving instructions to heat your home.
Parts commonly replaced
- Control unit
- Wiring harness
- Display fascia
Related codes
Fd Your boiler's reset function has been triggered inadvertently, meaning it just needs to be restarted to resume normal operation.
Your boiler's reset function has been triggered inadvertently, meaning it just needs to be restarted to resume normal operation.
What to check first
- Locate the reset button on the front control panel.
- Press and hold the button for 2 to 5 seconds.
- Wait a few minutes for the boiler to complete its restart sequence.
G2 Your boiler has detected an issue with the cold water arriving at the unit, meaning it cannot safely heat water for your taps or shower.
Your boiler has detected an issue with the cold water arriving at the unit, meaning it cannot safely heat water for your taps or shower.
What to check first
- Check that the main water stopcock in your home is fully open.
- Ensure any isolation valves on the pipework leading to the boiler are turned to the 'on' position.
- Check with your local water provider to see if there is a supply outage or burst pipe in your area.
Parts commonly replaced
- Inlet water filter
- Inlet pressure sensor
- Flow turbine
Related codes
G5 Your boiler has failed to ignite or stay lit correctly, meaning it cannot provide heating or hot water until it is reset or repaired.
Your boiler has failed to ignite or stay lit correctly, meaning it cannot provide heating or hot water until it is reset or repaired.
Parts commonly replaced
- Ionisation probe
- Ignition electrode
- Gas valve
- PCB
Related codes
G9 Your boiler has detected that hot water is escaping through the safety overflow pipe, usually because the system is overheating or a valve has failed.
Your boiler has detected that hot water is escaping through the safety overflow pipe, usually because the system is overheating or a valve has failed.
Parts commonly replaced
- Pressure Relief Valve (PRV)
- Expansion Vessel
- Temperature Sensor
Related codes
H8 Your boiler is undergoing a manual reset process and should return to normal operation shortly unless a repeat fault occurs.
Your boiler is undergoing a manual reset process and should return to normal operation shortly unless a repeat fault occurs.
What to check first
- Wait approximately 30 seconds for the reset sequence to complete
- Ensure the reset button was pressed firmly if the code persists
- Monitor the boiler for any new fault codes after the reset finishes
Related codes
Incorrect water flow rate Your boiler is struggling to detect the flow of water needed to heat your taps, usually because the incoming water supply is restricted or a internal sensor is stuck.
Your boiler is struggling to detect the flow of water needed to heat your taps, usually because the incoming water supply is restricted or a internal sensor is stuck.
What to check first
- Check that the isolation valve on the cold water mains pipe leading to your boiler is fully open.
- Check all taps in your home to ensure you have normal mains water pressure.
- Restart the boiler using the reset button to see if it clears the temporary fault.
Parts commonly replaced
- Water section diaphragm
- Flow switch
- Microswitch
Incorrect water temperature Your boiler is struggling to control the temperature of the water, which means it cannot reliably provide hot water or heating.
Your boiler is struggling to control the temperature of the water, which means it cannot reliably provide hot water or heating.
Parts commonly replaced
- Water diaphragm
- Gas valve
- NTC sensor
Related codes
Main burner will not light Your boiler is failing to ignite the flame needed to heat your water, which could be caused by blocked gas flow or a worn internal component.
Your boiler is failing to ignite the flame needed to heat your water, which could be caused by blocked gas flow or a worn internal component.
Parts commonly replaced
- Water section diaphragm
- Gas valve
- Microswitch
Noise Your boiler is struggling to pass water through its heating system, which is causing it to make loud, rumbling, or banging noises.
Your boiler is struggling to pass water through its heating system, which is causing it to make loud, rumbling, or banging noises.
Parts commonly replaced
- Heat exchanger
- Pump
- Diverter valve
Related codes
Your boiler is currently just starting up and running through its routine safety checks, so you do not need to take any action yet.
P8 Your boiler has detected that the water pressure inside the system is too high, which can cause safety valves to leak or the unit to shut down.
Your boiler has detected that the water pressure inside the system is too high, which can cause safety valves to leak or the unit to shut down.
What to check first
- Check that the filling loop valves are fully closed
- Bleed a radiator to release excess water pressure
- Monitor the pressure gauge stays between 1 and 1.5 bar
- Ensure the pressure relief valve is not dripping outside
Parts commonly replaced
- Pressure Relief Valve (PRV)
- Expansion Vessel
- Filling Loop