Ryan Gill, Engineer

31 Jan : Updated 6 Sep ● 43 min read

Worcester fault codes

Worcester Bosch boilers are undoubtedly the best around. They outshine many other big boiler brands when it comes to their popularity, but why? They’re efficient, reliable, and award-winning – consistently taking first place in the Which? Gas Boiler and Best Buy reports.

As with any boiler though, problems can start to present themselves. Some issues are more common than others when it comes to Worcester boiler problems. So it’s worth getting clued up about how to identify these in advance!

This way, when you notice your boiler acting up, you can think logically to decide whether the issue is detrimental to your boiler’s health - or easy to solve.

CDI Classic Combi / CDI Highflow Combi

Fault code	System behaviour	What to do?
A1	There could be: a potential water leak or that your pump either needs replacing or freeing due to the pump running dry and may have become stuck.	The best thing to do is to bleed your radiators and check your boiler pressure. If the fault code is still showing once you’ve done so, contact Worcester Bosch or BOXT so someone can take a further inspection. View A1 error code video
A7	This means that the hot water sensor or connecting leads need checking to make sure they are connected correctly.	Please contact Worcester Bosch or BOXT so someone can take a further inspection.
A8	This means that there has been a break in communication to FX sensor controls. Therefore your electrical connections need checking.	Unfortunately, you won’t be able to fix this problem. Please contact Worcester Bosch or BOXT so someone can take a further inspection.

CDI Classic Combi / CDI Highflow Combi / CDi Classic Regular

Fault code	System Behaviour	What to do?
B1	This means that the code plug is not being detected.	If the fault is still showing the fault after you’ve pressed ‘reset’ please contact Worcester Bosch or BOXT so someone can take a further inspection.
C6	This means that the speed of the fan is too low.	The fan lead and connector needs an inspection and possibly replacing. Unfortunately, you won’t be able to fix this problem. Please contact Worcester Bosch or BOXT so someone can take a further inspection.
E2	This means that there is an issue with the central heating. The (NTC) sensor may also be defective.	Unfortunately, you won’t be able to fix this problem. Please contact Worcester Bosch or BOXT so someone can take a further inspection.
E9	This means there could be an issue with the system pressure as the safety temperature limiter in central heating flow has been tripped.	If the fault is still showing the fault after you’ve pressed ‘reset’ please contact Worcester Bosch or BOXT so someone can take a further inspection.
EA	This means there may be an issue regarding flame loss.	The first thing you should do is to examine if other gas appliances in your home are working normally, that way you’ll know for sure if there is a gas supply in the property. It’s worth checking that the gas supply is on at the meter, if the boiler still doesn’t turn on - then contact Worcester Bosch or BOXT.
F0	This fault code symbolises an internal error within the boiler system.	If the fault is still showing the fault after you’ve pressed ‘reset’ please contact Worcester Bosch or BOXT so someone can take a further inspection.
F7	This symbolises that a flame has been detected, even though the appliance is switched off.	Don’t be tempted to reset your boiler, instead, contact Worcester Bosch or BOXT so someone can take a further inspection.
FA	This means that a flame has been detected even after the gas has been shut off.	The gas valve needs checking. Unfortunately, you won’t be able to fix this problem. Please contact Worcester Bosch or BOXT so someone can take a further inspection.
FD	This means that the ‘reset’ button has been pressed accidentally.	To fix this, try pressing the ‘reset’ button again. If the problem persists, contact Worcester Bosch or BOXT so someone can't take a further inspection.

CDI Highflow Combi

Fault code	System behaviour	What to do?
A5	This means that there is an issue with the Tank negative thermistor coefficient (NTC) and may be defective.	Unfortunately, you won’t be able to fix this problem. Please contact Worcester Bosch or BOXT so someone can take a further inspection.
D3	This means that the external temperature limiter switch is defective and may need to be replaced.	Unfortunately, you won’t be able to fix this problem. Please contact Worcester Bosch or BOXT to take a further inspection.
D5	This means there is a condensate pump failure.	This means the pump will need replacing. Unfortunately, you won’t be able to fix this problem. Please contact Worcester Bosch or BOXT to take a further inspection.
D6	This means there is an Internal heat bank overflow.	Unfortunately, you won’t be able to fix this problem. Please contact Worcester Bosch or BOXT to take a further inspection.
F1	This means there is a ROM fault.	Unfortunately, you won’t be able to fix this problem. Please contact Worcester Bosch or BOXT to take a further inspection.

CDi Compact / Greenstar 25/30 Si Combi / Greenstar 27/30 I system

Fault code	System behaviour	What to do?
T1	This means that the boiler is undertaking an ignition test and is therefore in test mode.	The boiler should return to normal operation once complete. If the issue persists, please contact Worcester Bosch or BOXT to take a further inspection.
T2	This means that the boiler is undertaking a fan test and is therefore in test mode.	The boiler should return to normal operation once complete. If the issue persists, please contact Worcester Bosch or BOXT to take a further inspection.
T3	This means that the boiler is undertaking a pump test and is therefore in test mode.	The boiler should return to normal operation once complete. If the issue persists, please contact Worcester Bosch or BOXT to take a further inspection.
T4	This means that the boiler is undertaking a three way valve test and is therefore in test mode.	The boiler should return to normal operation once complete. If the issue persists, please contact Worcester Bosch or BOXT to take a further inspection.
T6	This means that the boiler is undertaking an ionisation oscillator test and is therefore in test mode.	The boiler should return to normal operation once complete. If the issue persists, please contact Worcester Bosch or BOXT to take a further inspection.
9A 362	This means that an incorrect Heat Control Module (HCM) has been installed.	Unfortunately, you won’t be able to fix this problem. Please contact Worcester Bosch or BOXT to take a further inspection.
C6 215	This signifies the fan speed is too high.	Turn the boiler’s power off and on again. Once you’ve done this, if your boiler still isn’t operating correctly, then contact BOXT or Worcester Bosch.
EA 227	1).This signifies that no flame has been detected. This means there could be an issue with the gas valve (where the gas comes through) and may need replacing or adjusting. 2). Another reason for the fault code is there could be a blockage in siphon or the condensate discharge, check not frozen or blocked. 3) There may also be damage to the electrode or Ignition lead, without these parts a flame can’t be made. 4). Lastly, it could be an internal leak onto an electrical component.	Unfortunately, this isn’t something you’ll be able to fix yourself, so please contact BOXT or Worcester Bosch to send out an engineer. If you spot a leak, turn off your boiler and contact Worcester Bosch or BOXT. to get the components replaced.
F7 228	This means there is a flame error.	The best thing to do is to try and reset the system, if the issue persists then please contact Worcester Bosch or BOXT to take a further inspection.
FA 364	This means there is a gas valve leak.	You should turn off your boiler and contact BOXT or Worcester Bosch to send out an engineer.
FB 365	An FB 365 fault code means there is a gas valve leak.	You should turn off your boiler and contact BOXT or Worcester Bosch to send out an engineer.
A1 281	This means the pump is stuck or running with air in the system.	You should try and reset your boiler, if the issue persists, contact BOXT or Worcester Bosch to send out an engineer.
EF 349	This means that the boiler is operating at a minimum burner load.	Ensure that the system pressure is between 1 and 1.5 bar. If the issue continues, then contact either Worcester Bosch or BOXT.
NO CODE 212	This means the safety or flow temperature is rising too fast.	Try and reset your boiler, if the error continues then contact either Worcester Bosch or BOXT to send out an engineer.

CDi Compact / Greenstar 25/30 Si Combi / Greenstar 27/30 I system / Greenstar I System / Comb / GB162

Fault code	System behaviour	What to do?
FA 306	This means there is a false flame fault.	Try to reset your boiler, if it doesn’t reset then then contact Worcester Bosch or BOXT.
FD 231	This signifies a mains power fault or that the power has been interrupted during a lockout.	Try to reset your boiler, if the code still persists then you’ll need to contact an electrician or your electricity provider.
C1 264	This means that the airflow stopped during operation.	Try and reset your boiler, if the issue persists then contact either BOXT or Worcester Bosch to send out an engineer.
C4 273	This means that airflow has been present during the last 24 hours. Or there may be an issue with the fan operation.	Unfortunately, you won’t be able to fix this problem. Please contact Worcester Bosch or BOXT so someone can take a further inspection.
D1 240	This means that the return sensor has a short circuit.	Try and reset your boiler, if the issue persists then contact either BOXT or Worcester Bosch to send out an engineer.
E9 224	This means the fault Max thermostat has been activated.	Try and reset your boiler, if the issue persists then contact either BOXT or Worcester Bosch to send out an engineer.
E2 222	This means there is a flow sensor short circuit error.	This isn’t something you’ll be able to fix, please contact Worcester Bosch or BOXT to take a further inspection.
C7 214	The fault code C7 214 means that the fan isn’t running properly.	Unfortunately, you won’t be able to fix this problem. Please contact Worcester Bosch or BOXT to take a further inspection.
B7 257	This means there is an internal error in the boiler and a possible control board problem.	Please contact Worcester Bosch or BOXT to take a further inspection.
9U 233	This means the control box or heat control module (HCM) is defective or loose.	This isn’t something you’ll be able to fix. Contact BOXT or Worcester Bosch for an engineer call out.

Greenstar I System / Combi / GB162

Fault code	System behaviour	What to do?
226	This means the service tool has been connected in the blocking error history menu.	Try and reset your boiler, if the error continues then contact either Worcester Bosch or BOXT to send out an engineer.
C7 217	This means the fan has stopped operating properly.	This isn’t something you’ll be able to fix. Contact BOXT or Worcester Bosch for an engineer call out.
E9 276	This means that the primary flow temperature has exceeded 95°c.	Check the pressure is between 1.0 and 1.5 bar. Try to reset the boiler, if the issue still persists, then contact BOXT or Worcester Bosch for an engineer call out.
EA 229	This means there has been a loss of ionisation signal during operation.	Check the pressure is between 1.0 and 1.5 bar. Try to reset the boiler, if the issue still persists, then contact BOXT or Worcester Bosch for an engineer call out.
EA 261	This means the test control module (HCM) is potentially defective.	Try to reset the boiler, if the issue still persists, then contact BOXT or Worcester Bosch for an engineer call out.
F0 238	This means there’s a gas valve or control box error. It could also mean the burner control unit KIM (boiler identification module) is faulty.	Double check the system pressure is between 1.0 and 1.5 bar. Also, you should check that any other gas appliances are working as normal, to confirm that your gas supply is present. Once you’ve done this and your boiler still isn’t operating correctly, then contact BOXT or Worcester Bosch.
F0 239	This means the control box or the heat control module (HCM) is defective	This may be an electrical issue, so please contact BOXT or Worcester Bosch for an engineer call out.
EH 258	This means the control box or the heat control module (HCM) is defective.	This isn’t something you’ll be able to fix. Contact BOXT or Worcester Bosch for an engineer call out.
F0 272	This means the control box or the heat control module (HCM) is defective.	This isn’t something you’ll be able to fix. Contact BOXT or Worcester Bosch for an engineer call out.
F0 280	This means the control box or the heat control module (HCM) is defective.	This isn’t something you’ll be able to fix. Contact BOXT or Worcester Bosch for an engineer call out.
F0 290	This means that there is an issue with the control box as it may not have been installed properly and will potentially need replacing.	This isn’t something you’ll be able to fix. Contact BOXT or Worcester Bosch for an engineer call out.
235	This signifies there is an incompatible heat control module (HCM), meaning the control box needs the latest software.	Unfortunately, this isn’t you’ll be able to fix. Please contact Worcester Bosch or BOXT for an engineer call out.
360	This means the heat control module (HCM) is void. The current HCM doesn’t correlate with the control box.	Please contact Worcester Bosch or BOXT for an engineer call out.

CDi Compact / Greenstar 25/30 Si Combi / Greenstar 27/30 I system / GB162

Fault code	System behaviour	What to do?
E5 218	This means that the flow temperature is too high.	This isn’t something you’ll be able to fix, please contact Worcester Bosch or BOXT to take a further inspection.
E9 219	This means that there is a fault with the safety sensor.	Double check that your pressure is between 1 and 1.5 bar. If it is and code persists, please contact Worcester Bosch or BOXT to take a further inspection.
D4 271	This means that the temperature difference between flow and safety sensor has exceeded the limit.	Try and reset your boiler, if the issue persists then contact either BOXT or Worcester Bosch to send out an engineer.

Greenstar I System / Combi

Fault code	System behaviour	What to do?
C7 216	This means the fan speed is too low.	This isn’t something you’ll be able to fix. Contact BOXT or Worcester Bosch for an engineer call out.
E2 233	This means that the flow temperature sensor is disconnected.	Try to reset the boiler, if the issue still persists, then contact BOXT or Worcester Bosch for an engineer call out
E2 350	This means that the temperature flow sensor has shortened.	Check the pressure is between 1.0 and 1.5 bar. Try to reset the boiler, if the issue still persists, then contact BOXT or Worcester Bosch for an engineer call out.
E2 351	This means that the temperature flow sensor has shortened.	Check the pressure is between 1.0 and 1.5 bar. Try to reset the boiler, if the issue still persists, then contact BOXT or Worcester Bosch for an engineer call out.
C4 237	This means the control box or heat control module (HCM) is defective or loose.	This isn’t something you’ll be able to fix. Contact BOXT or Worcester Bosch for an engineer call out.
F0 242	This means the control box or the heat control module (HCM) is defective.	This may be an electrical issue, so please contact BOXT or Worcester Bosch for an engineer call out.
F0 258	This means the control box or the heat control module (HCM) is defective.	This isn’t something you’ll be able to fix. Contact BOXT or Worcester Bosch for an engineer call out.
F1 259	means the control box or the heat control module (HCM) is defective.	This isn’t something you’ll be able to fix. Contact BOXT or Worcester Bosch for an engineer call out.
F0 262	This means the control box or the heat control module (HCM) is defective.	This isn’t something you’ll be able to fix. Contact BOXT or Worcester Bosch for an engineer call out.
F1 263	This means the control box or the heat control module (HCM) is defective.	This isn’t something you’ll be able to fix. Contact BOXT or Worcester Bosch for an engineer call out.
328	This means there is an internal error with the mains voltage.	This isn’t something you’ll be able to fix. Contact BOXT or Worcester Bosch for an engineer call out.
356	This means there is an issue with the low mains voltage.	This isn’t something you’ll be able to fix. Please contact Worcester Bosch or BOXT for an engineer call out.
A8 362	This means there is an issue with the low mains voltage.	Please contact Worcester Bosch or BOXT for an engineer call out.
CC 800	This means there is an issue with the outdoor sensor.	Please contact Worcester Bosch or BOXT for an engineer call out.
D4 341	This means the primary flow temperature is rising too fast.	This isn’t something you’ll be able to fix. Please contact Worcester Bosch or BOXT for an engineer call out.

GB162

Fault code	System behaviour	What to do?
208	This means that the boiler is currently in chimney sweep mode.	This isn’t something you’ll be able to fix. Please contact Worcester Bosch or BOXT for an engineer call out.
200	This means that the boiler is in heating mode.	This isn’t something you’ll be able to fix. Please contact Worcester Bosch or BOXT for an engineer call out.
201	The boiler is in domestic hot water (DHW) mode.	This isn’t something you’ll be able to fix. Please contact Worcester Bosch or BOXT for an engineer call out.
202	The boiler is waiting – there was a heat demand from the on off or modulating control.	This isn’t something you’ll be able to fix. Please contact Worcester Bosch or BOXT for an engineer call out.
203	The boiler is on standby.	This isn’t something you’ll be able to fix. Please contact Worcester Bosch or BOXT for an engineer call out.
204	The boiler is waiting – the actual temperature is higher than the calculated or selected boiler temperature.	This isn’t something you’ll be able to fix. Please contact Worcester Bosch or BOXT for an engineer call out.
212	The temperature recorded by the flow temperature sensor or the safety sensor is rising too quickly.	This isn’t something you’ll be able to fix. Please contact Worcester Bosch or BOXT for an engineer call out.
260	The flow temperature sensor is not detecting a rise in temperature following a burner start.	This isn’t something you’ll be able to fix. Please contact Worcester Bosch or BOXT for an engineer call out.
265	The boiler is waiting in response to a heat demand – the boiler regularly switches to partial load.	This isn’t something you’ll be able to fix. Please contact Worcester Bosch or BOXT for an engineer call out.
268	This means the boiler is in a component test phase.	This isn’t something you’ll be able to fix. Please contact Worcester Bosch or BOXT for an engineer call out.
270	The boiler is modulating upwards.	This isn’t something you’ll be able to fix. Please contact Worcester Bosch or BOXT for an engineer call out.
283	The boiler is preparing for a burner start – the fan and pump are activated.	This isn’t something you’ll be able to fix. Please contact Worcester Bosch or BOXT for an engineer call out.
284	This means the gas valve has switched.	This isn’t something you’ll be able to fix. Please contact Worcester Bosch or BOXT for an engineer call out.
305	The boiler is waiting for domestic hot water (DHW) operation to end	Try to reset the boiler, if the issue still persists, then contact BOXT or Worcester Bosch for an engineer call out
9A 361	The burner control unit that has been fitted is not compatible with the KIM (boiler identification module).	This isn’t something you’ll be able to fix. Please contact Worcester Bosch or BOXT for an engineer call out.
A3 317	This means there is a short circuit in the flue gas temperature sensor contacts.	This isn’t something you’ll be able to fix. Please contact Worcester Bosch or BOXT for an engineer call out.
C6 216	This means the fan speed is too low.	This isn’t something you’ll be able to fix. Please contact Worcester Bosch or BOXT for an engineer call out.
CE 207	This means that the water pressure is too low.	Try and top up the pressure so that the needle is between 1 and 1.5 bar. If the pressure continues to drop, contact BOXT or Worcester Bosch as you may have a leak.
CE 266	Pump test failed.	This isn’t something you’ll be able to fix. Please contact Worcester Bosch or BOXT for an engineer call out.
D1 241	The contacts of the boiler return temperature sensor have been interrupted.	This isn’t something you’ll be able to fix. Please contact Worcester Bosch or BOXT for an engineer call out.
D3 232	This means the external switching contact has opened.	This isn’t something you’ll be able to fix. Please contact Worcester Bosch or BOXT for an engineer call out.
D4 213	This means the actual temperature recorded by the flow temperature sensor or return temperature sensor is rising too quickly.	This isn’t something you’ll be able to fix. Please contact Worcester Bosch or BOXT for an engineer call out.
D4 286	This means the boiler return temperature sensor has detected a return temperature higher than 105°c.	This isn’t something you’ll be able to fix. Please contact Worcester Bosch or BOXT for an engineer call out.
E2 223	This means the flow temperature sensor contacts have been interrupted.	This isn’t something you’ll be able to fix. Please contact Worcester Bosch or BOXT for an engineer call out.
E9 210	This means the temperature measured by the flue gas sensor is too high and is open.	This isn’t something you’ll be able to fix. Please contact Worcester Bosch or BOXT for an engineer call out.
E9 220	This means the contacts for the safety temperature sensor have shorted or the safety temperature sensor has detected a temperature higher than 130°c.	This isn’t something you’ll be able to fix. Please contact Worcester Bosch or BOXT for an engineer call out.
E9 277	The safety temperature sensor has measured temperature in excess of 95°c.	This isn’t something you’ll be able to fix. Please contact Worcester Bosch or BOXT for an engineer call out.
E9 285	The boiler return temperature sensor has measured a temperature higher than 95°c.	This isn’t something you’ll be able to fix. Please contact Worcester Bosch or BOXT for an engineer call out.
E9 318	The flue gas temperature sensor contacts have been interrupted.	This isn’t something you’ll be able to fix. Please contact Worcester Bosch or BOXT for an engineer call out.
EA 234	The contacts of the gas valve have been interrupted.	This isn’t something you’ll be able to fix. Please contact Worcester Bosch or BOXT for an engineer call out.
EA 269	The ignition device has been activated for too long.	This isn’t something you’ll be able to fix. Please contact Worcester Bosch or BOXT for an engineer call out.
GB162	The ignition device has been activated for too long.	This isn’t something you’ll be able to fix. Please contact Worcester Bosch or BOXT for an engineer call out.
F0 278	The sensor test has failed – cabling and plug sensors need checking.	This isn’t something you’ll be able to fix. Please contact Worcester Bosch or BOXT for an engineer call out.
F0 279	The burner control unit, or KIM, is faulty – control unit may need replacing.	This isn’t something you’ll be able to fix. Please contact Worcester Bosch or BOXT for an engineer call out.
F0 287	The burner control unit, or KIM, has an error.	This isn’t something you’ll be able to fix. Please contact Worcester Bosch or BOXT for an engineer call out.
F7 328	A brief power failure has occurred.	This isn’t something you’ll be able to fix. Please contact Worcester Bosch or BOXT for an engineer call out.
EC 256	The burner control unit has an error.	This isn’t something you’ll be able to fix. Please contact Worcester Bosch or BOXT for an engineer call out.
H07	The current water pressure is too low, limiting the performance in heat mode as well as domestic hot water (DHW) mode.	This isn’t something you’ll be able to fix. Please contact Worcester Bosch or BOXT for an engineer call out.
rE	The boiler resets.	Wait for the boiler to reset, if the issue still persists - then please contact Worcester Bosch or BOXT for an engineer call out.

CDI Highflow Combi / Greenstar Ri

Fault code

System behaviour

What to do?

Light off

This means there’s no boiler demand or there’s no power at the control board.

Try to reset your boiler, if the issue persists then contact Worcester Bosch or BOXT for an engineer call out.

Light on

CDI Highflow Combi - This means the heating demand on the boiler is OK.

Greenstar Ri - This means the appliance is on but not operating during demand.

Try to reset your boiler, if the issue persists then contact Worcester Bosch or BOXT for an engineer call out.

Greenstar Ri and Ri Compact

Fault code	System behaviour	What to do?
1 flash 5 seconds off	This means no ionisation has been detected after the ignition.	Try to reset your boiler. You can do this by turning the control knob anti-clockwise to reset the position. If the issue persists then contact Worcester Bosch or BOXT for an engineer call out.
2 flashes 5 seconds off	This means there has been a loss of ionisation signal during the operation of the boiler.	Try to reset your boiler. You can do this by turning the control knob anti-clockwise to reset the position. If the issue persists then contact Worcester Bosch or BOXT for an engineer call out.
3 flashes 5 seconds off	This means there is a gas valve error.	Try to reset your boiler. You can do this by turning the control knob anti-clockwise to reset the position. If the issue persists then contact Worcester Bosch or BOXT for an engineer call out.
4 flashes 5 seconds off	First safety timing error / ignition timing error.	Try to reset your boiler. You can do this by turning the control knob anti-clockwise to reset the position. If the issue persists then contact Worcester Bosch or BOXT for an engineer call out.
5 flashes 5 seconds off	Slow flashes tend to be an ignition lock out.	Try to reset your boiler. You can do this by turning the control knob anti-clockwise to reset the position. If the issue persists then contact Worcester Bosch or BOXT for an engineer call out.
4 flashes 5 second gap 1 long flash.	This means the sensor test failed.	Try to reset your boiler. You can do this by turning the control knob anti-clockwise to reset the position. If the issue persists then contact Worcester Bosch or BOXT for an engineer call out.
4 flashes, 5 second gap, 2 long flashes	This means the safety temperature is too high.	Try to reset your boiler. You can do this by turning the control knob anti-clockwise to reset the position. If the issue persists then contact Worcester Bosch or BOXT for an engineer call out.
4 flashes, 5 second gap, 3 long flashes	This means the max safety thermostat has been activated.	Try to reset your boiler. You can do this by turning the control knob anti-clockwise to reset the position. If the issue persists then contact Worcester Bosch or BOXT for an engineer call out.
4 flashes, 5 second gap, 4 long flashes	The return temperature is too high.	Try to reset your boiler. You can do this by turning the control knob anti-clockwise to reset the position. If the issue persists then contact Worcester Bosch or BOXT for an engineer call out.
4 flashes, 5 second gap, 5 long flashes	The flow temperature is too high – supply sensor exceeded 110°c.	Try to reset your boiler. You can do this by turning the control knob anti-clockwise to reset the position. If the issue persists then contact Worcester Bosch or BOXT for an engineer call out.
1 long flash, 4 quick flashes, 5 second gap, 1 long flash, 4 quick flashes	Heating control module (HCM) defective.	Try to reset your boiler. You can do this by turning the control knob anti-clockwise to reset the position. If the issue persists then contact Worcester Bosch or BOXT for an engineer call out.
2 long flashes, 4 quick flashes, 5 second gap, 2 long flashes, 4 quick flashes	This means there is an issue with the fan.	Try to reset your boiler. You can do this by turning the control knob anti-clockwise to reset the position. If the issue persists then contact Worcester Bosch or BOXT for an engineer call out.
3 long flashes, 4 quick flashes, 5 second gap, 3 long flashes, 4 quick flashes	This means the mains voltage is interrupted after locking error.	Try to reset your boiler. You can do this by turning the control knob anti-clockwise to reset the position. If the issue persists then contact Worcester Bosch or BOXT for an engineer call out.
4 long flashes, 4 quick flashes, 5 second gap, 4 long flash, 4 quick flashes	Internal control board faults.	Try to reset your boiler. You can do this by turning the control knob anti-clockwise to reset the position. If the issue persists then contact Worcester Bosch or BOXT for an engineer call out.
5 long flashes, 4 quick flashes, 5 second gap, 5 long flash, 4 quick flashes	All other miscellaneous faults.	Try to reset your boiler. You can do this by turning the control knob anti-clockwise to reset the position. If the issue persists then contact Worcester Bosch or BOXT for an engineer call out.

Greenstar Ri

Fault code	System behaviour	What to do?
Slow flash ( mostly off flashes on)	Ignition lockout.	Try to reset your boiler. You can do this by turning the control knob anti-clockwise to reset the position. If the issue persists then contact Worcester Bosch or BOXT for an engineer call out.
Slow flash ( mostly on flashes off)	Flue overheat or heat exchanger overheat.	Try to reset your boiler. You can do this by turning the control knob anti-clockwise to reset the position. If the issue persists then contact Worcester Bosch or BOXT for an engineer call out.
Fast flash	Volatile lockout sensor fan or code plug.	Try to reset your boiler. You can do this by turning the control knob anti-clockwise to reset the position. If the issue persists then contact Worcester Bosch or BOXT for an engineer call out.
2 pulses	Check service mode switch is in the minimum position.	Try to reset your boiler. You can do this by turning the control knob anti-clockwise to reset the position. If the issue persists then contact Worcester Bosch or BOXT for an engineer call out.
5 pulses	Check service mode switch is in the max position.	Try to reset your boiler. You can do this by turning the control knob anti-clockwise to reset the position. If the issue persists then contact Worcester Bosch or BOXT for an engineer call out.

Greenstar 8000

Fault code	System behaviour	What to do?
200 O	This means the boiler is in heating mode.	Try to reset your boiler. You can do this by turning the control knob anti-clockwise to reset the position. If the issue persists then contact Worcester Bosch or BOXT for an engineer call out.
202 O	This means the boiler is in anti-cycle mode.	Try to reset your boiler. You can do this by turning the control knob anti-clockwise to reset the position. If the issue persists then contact Worcester Bosch or BOXT for an engineer call out.
203 0	This means the boiler is in standby – no heat energy demand.	Try to reset your boiler. You can do this by turning the control knob anti-clockwise to reset the position. If the issue persists then contact Worcester Bosch or BOXT for an engineer call out.
204 O	This means the current primary water temperature is higher than set value.	Try to reset your boiler. You can do this by turning the control knob anti-clockwise to reset the position. If the issue persists then contact Worcester Bosch or BOXT for an engineer call out.
208 0	This signifies the boiler is in chimney sweep demand.	Try to reset your boiler. You can do this by turning the control knob anti-clockwise to reset the position. If the issue persists then contact Worcester Bosch or BOXT for an engineer call out.
224 V	This means the safety temperature limiter has tripped.	Try top-up water until the reset pressure is reached. If the issue persists then contact Worcester Bosch or BOXT for an engineer call out.
227 V	This means no flame signal after the ignition burner. The control unit may need replacing.	Try to reset your boiler. You can do this by turning the control knob anti-clockwise to reset the position. If the issue persists then contact Worcester Bosch or BOXT for an engineer call out.
228 V	This signifies there is a flame signal without a flame present. The air/gas ratio control valve may need replacing.	Try to reset your boiler. You can do this by turning the control knob anti-clockwise to reset the position. If the issue persists then contact Worcester Bosch or BOXT for an engineer call out.
305 0	The boiler is in hot water anti-cycle mode.	Try to reset your boiler. You can do this by turning the control knob anti-clockwise to reset the position. If the issue persists then contact Worcester Bosch or BOXT for an engineer call out.
306 V	Issue with the flame signal after closing the fuel supply. The air/gas ratio control valve might need replacing.	Try to reset your boiler. You can do this by turning the control knob anti-clockwise to reset the position. If the issue persists then contact Worcester Bosch or BOXT for an engineer call out.
815 W/B	The low loss header temperature sensor is faulty. Check the sensor port or the differential sensor. May be installed incorrectly or damaged.	Try to reset your boiler. You can do this by turning the control knob anti-clockwise to reset the position. If the issue persists then contact Worcester Bosch or BOXT for an engineer call out.
1010 O	This means there is no BUS communication cable, EMS-Bus isn’t connected or damaged – connect the cable for the EMS-Bus or replace the damaged cable exchange fuse.	Try to reset your boiler. You can do this by turning the control knob anti-clockwise to reset the position. If the issue persists then contact Worcester Bosch or BOXT for an engineer call out.
1017 W	This means the water pressure is too low – the water needs topping up and the vent system or pressure sensor may need replacing.	Try topping up your pressure. If the issue persists then contact Worcester Bosch or BOXT for an engineer call out.
1021 B	The hot water temperature sensor is defective – the plug to the hot water temperature sensor may not be connected.	Try to reset your boiler. You can do this by turning the control knob anti-clockwise to reset the position. If the issue persists then contact Worcester Bosch or BOXT for an engineer call out.
1022 B	This means the hot water storage temperature sensor is defective.	Try to reset your boiler. You can do this by turning the control knob anti-clockwise to reset the position. If the issue persists then contact Worcester Bosch or BOXT for an engineer call out.
1037 W	This means the outside temperature sensor is defective – check the connecting lead.	Try to reset your boiler. You can do this by turning the control knob anti-clockwise to reset the position. If the issue persists then contact Worcester Bosch or BOXT for an engineer call out.
1065 B	This means the pressure sensor is defective or not connected – check pressure sensor connection as it may need replacing.	Try to reset your boiler. You can do this by turning the control knob anti-clockwise to reset the position. If the issue persists then contact Worcester Bosch or BOXT for an engineer call out.
1068 W	The outside temperature sensor is defective – check the connecting lead.	Try to reset your boiler. You can do this by turning the control knob anti-clockwise to reset the position. If the issue persists then contact Worcester Bosch or BOXT for an engineer call out.
1073 W	This means the temperature sensor may need replacing.	Try to reset your boiler. You can do this by turning the control knob anti-clockwise to reset the position. If the issue persists then contact Worcester Bosch or BOXT for an engineer call out.
1074 W	This means there is no signal from the flow temperature sensor available – connect the plug to the flow temperature sensor correctly or the temperature sensor could need replacing.	Try to reset your boiler. You can do this by turning the control knob anti-clockwise to reset the position. If the issue persists then contact Worcester Bosch or BOXT for an engineer call out.
1075 W	Short circuit of the temperature sensor at the heating block – temperature sensor may need replacing.	Try to reset your boiler. You can do this by turning the control knob anti-clockwise to reset the position. If the issue persists then contact Worcester Bosch or BOXT for an engineer call out.
1076 W	This means there is no signal from the temperature sensor at the heating block available – replace the temperature sensor, the connecting lead or the control unit.	Try to reset your boiler. You can do this by turning the control knob anti-clockwise to reset the position. If the issue persists then contact Worcester Bosch or BOXT for an engineer call out.
2920 V	This signifies there is an error with the flame monitoring.	Try to reset your boiler. You can do this by turning the control knob anti-clockwise to reset the position. If the issue persists then contact Worcester Bosch or BOXT for an engineer call out.
2924 V	This signifies there is no feedback from the modulating gas valve. The gas valve relay is defective – press the reset button and apply burner start, wait to see if fault reoccurs, if it does the gas valve needs replacing.	Try to reset your boiler. You can do this by turning the control knob anti-clockwise to reset the position. If the issue persists then contact Worcester Bosch or BOXT for an engineer call out.
2925 V	This means the feedback from the modulating gas valve is too low.	Try to reset your boiler. You can do this by turning the control knob anti-clockwise to reset the position. If the issue persists then contact Worcester Bosch or BOXT for an engineer call out.
2927 B	This means the flame failed during burner operation.	Try to reset your boiler. You can do this by turning the control knob anti-clockwise to reset the position. If the issue persists then contact Worcester Bosch or BOXT for an engineer call out.
2946 V	This means the incorrect code plug has been detected – the code plug needs replacing.	Try to reset your boiler. You can do this by turning the control knob anti-clockwise to reset the position. If the issue persists then contact Worcester Bosch or BOXT for an engineer call out.
2948 B	This means there is no flame signal. If the fault occurs repeatedly, the setting of the CO2 valves need checking.	Try to reset your boiler. You can do this by turning the control knob anti-clockwise to reset the position. If the issue persists then contact Worcester Bosch or BOXT for an engineer call out.
2950 B	This means there is no flame signal.	Try to reset your boiler. You can do this by turning the control knob anti-clockwise to reset the position. If the issue persists then contact Worcester Bosch or BOXT for an engineer call out.
2963 B	This means the signal from the flow and heat exchanger temperature sensor is outside of range.	Try to reset your boiler. You can do this by turning the control knob anti-clockwise to reset the position. If the issue persists then contact Worcester Bosch or BOXT for an engineer call out.
2964 B	This means the flow rate in the heat exchanger is too low.	Try to reset your boiler. You can do this by turning the control knob anti-clockwise to reset the position. If the issue persists then contact Worcester Bosch or BOXT for an engineer call out.
2965 B	This means the flow temperature is too high.	Try to reset your boiler. You can do this by turning the control knob anti-clockwise to reset the position. If the issue persists then contact Worcester Bosch or BOXT for an engineer call out.
966 B	This means the flow temperature rise in the heat exchanger is too rapid.	Try to reset your boiler. You can do this by turning the control knob anti-clockwise to reset the position. If the issue persists then contact Worcester Bosch or BOXT for an engineer call out.
2967 B	This means the flow / heat exchanger temperature sensor differential is too great.	Try to reset your boiler. You can do this by turning the control knob anti-clockwise to reset the position. If the issue persists then contact Worcester Bosch or BOXT for an engineer call out.
2970 B	This means the pressure drop in the heating system is too rapid.	Try to reset your boiler. You can do this by turning the control knob anti-clockwise to reset the position. If the issue persists then contact Worcester Bosch or BOXT for an engineer call out.
2971 B	The system pressure too low – the heating system needs venting or water needs topping up until the preset pressure is reached. Replace the cable to the pressure sensor and replace the pressure sensor.	Try to reset your boiler. You can do this by turning the control knob anti-clockwise to reset the position. If the issue persists then contact Worcester Bosch or BOXT for an engineer call out.

That should shed a bit more light on your situation. But if you’re still concerned, give BOXT a ring and we’ll have a chat with you to discuss further. From 8am - 8pm every weekday, we’re here to help you get your boiler up and running again. Call us for free on this number, 0800 193 7777.

Alternatively, if you haven’t got time for that - you can ask us anything on our Live Chat. Pick the brains of our senior engineers who work hard to guide you through any boiler problems.

How can you identify Worcester faults?

All Worcester Bosch boilers installed in the last decade will have a control panel on the front clearly displaying Worcester boiler fault codes. Most codes will appear as a Worcester boiler EA fault, though occasionally these may differ. You can easily find and reference these to pinpoint the error at hand by looking in your boiler manual or checking online.

Some boiler issues can develop and cause serious damage further down the line. Here are some quick regular checks you can do to identify any potential Worcester boilers problems:

Is your thermostat timer and temperature gauge set correctly?
Is your boiler pressure at a normal level?
Are all the appliances around your home receiving a gas supply?
Is there a blue light showing on the front of your boiler? If so, there will be an error to investigate.
Are there any Worcester boiler error codes being displayed? The code will allow you to identify the issue easily.

Common Worcester fault codes

EA338 or A281 – A leak somewhere, either within your boiler or around the system.
A41 – Boiler making loud noises – likely due to a faulty pump or heat exchanger.
EA227 – Boiler has locked out. This will be to prevent any further damage occurring and to remove potential danger.
E5218, E5332, E9219, E9224, D1286 – Boiler has overheated.
EA225 or D5 – Condensate pipe is blocked.

Noticed a Worcester fault?

Worcester boiler faults tend to occur very rarely due to the quality and reputability of their components. As your boiler starts to get older and issues do start to show, you can use Worcester boiler error codes to diagnose the issue. It is important to keep in mind that the process of actually fixing any issues should be left to an engineer to be on the safe side.

Let’s investigate some of the more notable Worcester boiler problems, so if they arise, there’s no need to panic.

Boiler problem 1: no hot water

A lot of Worcester boiler faults are noticeable initially through having trouble heating your home. Worcester boiler problems with heating are often evident through the temperature of the water coming through your taps or within your radiators.

Battling through a chilly home due to your radiators not receiving any hot water? Only have lukewarm/cold water coming through your taps? These are clear signs of a fault or blockage somewhere within your heating system.

There are a few other things that may have gone wrong to mean you have to endure a cold shower.

Do you have a faulty diverter valve?

Diverter valves are not large components of your boiler, but don’t let their size fool you. This boiler component is responsible for controlling both the hot water flowing to your taps/showers and the hot water for your central heating system.

If it’s not faulty, a diverter valve should prioritise providing hot water to your taps and showers - over your central heating. So, as you turn a hot tap on, the valve should be tightly closed, preventing hot water from flowing to your heating pipes. This way, you can have optimum hot water for your taps and showers - rather than having to split the hot water with your radiators.

The problems can arise as your boiler gets older and the diverter valve starts to stick when opening and closing.

Don’t worry, Worcester Greenstar diverter valve problems are not something to worry about if you have a relatively new boiler. It’s when your boiler starts to age that it will be more prone to this occurring.

How to identify a faulty diverter valve

You have no heating but do have hot water. Or you have no hot water but do have heating. Either of these is a strong indicator that your diverter valve is stuck either open or closed.
Your tap water is lukewarm. This implies your valve is sticking as it closes so your taps/showers can’t receive the full heating power of your boiler.
Your central heating must be turned on for you to have hot water through the taps.

How to solve Worcester Greenstar diverter valve problems

Sadly, having a faulty diverter valve is not good news. The valves are not always the cheapest item to replace. This will of course have to be carried out by a Gas Safety Registered Engineer. If you add up the cost of a valve, the tools needed to do the job, and the hourly rate of a skilled engineer will be expensive.

Therefore, if you find your valve is sticking frequently and causing trouble - then this is a great time to begin looking for a replacement boiler.

Replacing your boiler doesn’t have to break the bank. It can be a surprisingly positive experience. Opting for a new Worcester Bosch boiler is likely to be cheaper than replacing such a small but essential component, especially if your boiler is becoming worse for wear anyway.

Don’t believe us? Take a few minutes to answer our quick and simple questions on the BOXT site, where we will find your perfect boiler match. You can even have it installed as soon as the next day!

Boiler problem 2: no heating

Are you finding your boiler isn’t turning on or functioning whatsoever? This is referred to as your boiler locking out. There are several potential causes of this. Your boiler may have gained or lost too much pressure or even lost power completely. All Worcester boilers are fitted with safeguards, which essentially prevent any risk or danger, by stopping your boiler in its tracks when a certain issue occurs.

After a boiler lock out, the Worcester boiler error code 227 will be displayed, so you can easily identify this issue and get it seen to as soon as possible.

Is your condensate pipe blocked?

All modern combi boilers by law must have a condensate pipe which vents any harmful flue gases from your home. Due to these pipes being outside, they can become blocked by debris or freeze during the winter months. This can cause issues like your boiler overheating and eventually locking out.

When this happens, simply use warm water to defrost the pipe if necessary or remove any blockages to allow flue gas to escape freely. Most issues are identifiable by a Worcester boiler EA fault – in this case, look out for the code EA225.

Boiler problem 3: pressure issues

When it comes to the issue of pressure within your boiler, the problem can be simple and easy to solve, or a lot more serious.

If you’ve noticed your boiler pressure rising or dropping gradually over time, this isn’t something to worry about. To boost your boiler pressure back to normal levels, you can follow the steps for re-pressurising or call out an engineer to help. For lowering pressure, you may need to have a go at bleeding your radiators to release any trapped air from your system.

More sudden and dramatic drops in boiler pressure can indicate a more pressing matter to deal with.

Is there a leak in your system?

Leaks can occur at any time within any area of your heating system, this can make them more difficult to spot! Look around your boiler, pipes, radiators, valves, and even your water pumps for any damp or swollen patches. Worcester Bosch fault codes to look out for to signal whether you have a leak are EA338 or A281.

Unfortunately, if the leak is within your boiler, there is a likelihood that there is a part that needs replacing. Whether this be certain release valves or your entire pipework. An engineer should examine this issue.

Are you having central heating pump problems?

Your central heating pump may be the culprit when it comes to locating a leak and fixing a sudden drop in boiler pressure. The valve seal on a pump will wear down over time naturally, especially if too much pressure is placed on it or there is a sudden increase in water flow.

As well as causing your boiler’s pressure to drop, your central heating pump problems can have the opposite effect. If a pump gets too hot due to an error, it will seize up, affecting the overall temperature of your boiler and wreaking havoc.

Whilst replacing your central heating pump is an option, if your boiler has reached a certain age, it won’t be worthwhile. With BOXT, you can replace your boiler at a highly competitive price, knowing you are investing in a boiler that will last many years – rather than spending money on your old boiler that is on the way out.

Whilst replacing your central heating pump is an option - after it’s reach a certain age it won’t be worthwhile. With BOXT, you can replace your boiler at a highly competitive price. Reliable, smooth, and consistent. BOXT boilers will last longer - giving you confidence in your home.

Boiler problem 4: hearing loud noises

Occasionally with a Worcester boiler, or any boiler for that matter, faults may be noticeable due to loud or unusual noises being produced. If you do hear some strange noises, look for Worcester boiler error codes to identify why this may be happening. Code A41 is a common code that presents itself when a boiler is making loud noises.

Again, this might be a result of a faulty water pump or an airlock in the pump. This will be preventing water from flowing through smoothly. Or, there could be an issue with your boiler heat exchanger, in this case your boiler is ‘kettling’. This noise occurs due to a build up of limescale or sludge on the heat exchanger, which restricts the water flow, causing the kettle-like noise. You don’t need to worry when this happens, as your boiler will use its built-in safeguards to lockout and remove any further risk.

You can attempt to power flush your boiler and fix this error, however it is usually a sign of needing a replacement heat exchanger. Consistent kettling problems will usually only occur in boilers that have been installed for a significant number of years. Consider replacing your boiler for a new Worcester Bosch model which comes with a 10 year warranty as standard. Enjoy peace of mind for the next decade, and save more money in the long run - rather than replacing old parts of an inefficient boiler.

Boiler problem 5: no power to boiler

In an instance of your boiler power cutting off: check your sockets in case they have tripped, your Printed Circuit Board (PCB), or your Residual Current Device (RCD) for any faults.

If you think there is a fault with any of these components, it’s essential that you call out an engineer to look closer. Again, it’s likely that power failures are a result of a more serious issue around your boiler that would be best solved by replacing your unit – and can be affordable.

Interested in replacing your boiler and avoiding recurrent worcester boiler problems?

If your Worcester boiler is one of the older models (over eight years old) it may well be time to opt for a new boiler. At BOXT, our specialists can advise you on whether you need a replacement and the right type of boiler for your home. If you’re seeking specific advice, speak to us via web chat or visit our site for more information.

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