Last updated on: 29 August 2024
List of Worcester Bosch Boiler Error Codes / Fault Codes With Effective Solutions
Although Worcester Bosch boilers are of high quality, problems can start to present themselves as with any boiler. Some issues are more common than others when it comes to Worcester Bosch boiler error codes. So it’s worth knowing how to identify these (and find solutions for them) in advance.
You can find some of the common Worcester Bosch boiler error codes, along with their solutions below.
1. CDI Classic Combi / CDI Highflow Combi Boiler Error Codes
2. Worcester Bosch CDI Compact / Greenstar 27/30 I System / Greenstar 25/30 SI Combi Boiler Error Codes
3. Worcester Bosch CDI Classic Regular Boiler Error Codes
4. Worcester Bosch Greenstar I System / Combi Boiler Error Codes
- 226
- FD-231
- C7 214
- C6 215
- C7 216
- C7 217
- C1 264
- C4 273
- E2 222
- E2 233
- E9 276
- E2 350
- E2 351
- FA 306
- EA 227
- F7 228
- EA 229
- EA 261
- 9U 233
- F0 238
- F0 239
- F0 242
- B7 257
- F0 258
- EH 258
- F1 259
- F0 262
- F1 263
- F0 272
- F0 280
- F0 290
- 328
- 235
- 356
- 360
- A8 362
- CC 800
- A1 281
- E9 224
- D4 341
5. Worcester Bosch GB162 Boiler Error Codes
- 208
- 200
- 201
- 202
- 203
- 204
- 212
- 226
- 260
- 265
- 268
- 270
- 283
- 284
- 305
- 235
- 360
- 9A 361
- 9U 233
- A3 317
- B7 257
- C1 264
- C4 273
- C6 215
- C6 216
- C7 214
- C7 217
- CE 207
- CE 266
- D1 240
- D1 241
- D3 232
- D4 213
- D4 271
- D4 286
- E2 222
- E2 223
- E5 218
- E9 210
- E9 219
- E9 220
- E9 224
- E9 276
- E9 277
- E9 285
- E9 318
- EA 227
- EA 229
- EA 234
- EA 261
- EA 269
- F0 238
- F0 239
- F0 242 – F0 253, and F0 255, F0 259, F0 263, F0 267, F0 272
- F0 278
- F0 279
- F0 280
- F0 287
- F0 290
- F7 228
- F7 328
- FA 306
- FD 231
- EC 256
- EH 258
- GB162
- H07
- HrE
- rE
6. Worcester Bosch Greenstar Ri Boiler Faults
- No light
- Light on
- Slow flash (mostly off flashes on)
- Slow flash (mostly on flashes off)
- Fast flash
- 2 pulses
- 5 pulses
7. Worcester Bosch Greenstar 8000 life Combi Boiler Error Codes
8. Worcester 4000 Error Codes
1. CDI Classic Combi / CDI Highflow Combi Boiler Error Codes
| Fault Code | System Behavior | Solution |
| A1 | Either water is leaking or the pump needs freeing or replacing due to the pump running dry. | The best course of action 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 so someone can take a further inspection. |
| A7 | The hot water negative thermistor coefficient (NTC) sensor is defective – the connecting leads or hot water sensor need checking. | Please contact Worcester Bosch so someone can take a further inspection. |
| A8 | There has been a break in communication with FX sensor controls. Therefore your electrical connections need checking. | Please contact Worcester Bosch so someone can take a further inspection. |
| B1 | Code plug not detected | Reset the boiler |
| C6 | This means that the fan speed is too low. | The fan lead and connector needs an inspection and possibly replacing. Please contact Worcester Bosch for a further inspection. |
| E2 | This means that there is a problem with the central heating. The (NTC) sensor might also be defective. | Please contact Worcester Bosch 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 the central heating flow has been tripped. | If you still see the fault after you’ve pressed ‘reset’ please contact Worcester Bosch for a further inspection |
| EA | There is a problem regarding flame loss. | First, you should examine if other gas appliances in your home are working normally so that you 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. |
| F0 | This fault code symbolises an internal error within the boiler system. | If the fault is still showing after you’ve pressed ‘reset’ please contact Worcester Bosch to get a further inspection. |
| F7 | A flame has been detected, although the appliance is not on. | Don’t be tempted to reset your boiler, instead, contact Worcester Bosch for a further inspection. |
| FA | A flame has been detected even after the gas was shut off. | The gas valve needs checking. Please contact Worcester Bosch to get a further inspection. |
| FD | The ‘reset’ button has been pressed accidentally. | Try pressing the ‘reset button again to fix this. However, if the problem persists, contact Worcester Bosch to get a further inspection. |
2. Worcester Bosch CDI Compact / Greenstar 27/30 I System / Greenstar 25/30 SI Combi Boiler Error Codes
| Fault Code | System Behavior | Solution |
| T1 | The boiler is undertaking an ignition test and is thus in test mode. | The boiler normally returns to normal operation once complete. If the problem persists, please contact Worcester Bosch for a further inspection. |
| T2 | The boiler is undertaking a fan test and is thus in test mode. | The boiler typically returns to normal operation once complete. If not, please contact Worcester Bosch for a further inspection. |
| T3 | The boiler is undertaking a pump test and is thus in test mode. | The boiler typically returns to normal operation once complete. If not, please contact Worcester Bosch for a further inspection. |
| T4 | The boiler is undertaking a three-way valve test and is thus in test mode. | The boiler typically returns to normal operation once complete. If not, please contact Worcester Bosch to get a further inspection. |
| T6 | The boiler is undertaking an ionisation oscillator test and is thus in test mode. | The boiler usually returns to normal operation once complete. If the issue persists, please contact Worcester Bosch to get a further inspection. |
| 9A 362 | An incorrect Heat Control Module (HCM) was installed. | Please contact Worcester Bosch to get a further inspection. |
| C6 215 | The fan speed is too high. | Turn the boiler’s power off and on again. Once you’ve done this, if your boiler still doesn’t operate correctly, then contact Worcester Bosch. |
| EA 227 | 1.) No flame has been detected. There could be an issue with the gas valve and may need adjusting or replacing. 2.) Another reason is there could be a blockage in the siphon or the condensate discharge, check not frozen or blocked. 3.) There may also be damage to the ignition or electrode lead; a flame can’t be made without them. 4.) It could also be an internal leak onto an electrical component. | Unfortunately, you cannot fix this yourself, so please contact Worcester Bosch for an engineer’s help. If you spot a leak, turn off your boiler and contact Worcester Bosch to get the components replaced. |
| F7 228 | There is a flame error. | You should try and reset the system, but contact Worcester Bosch for a further inspection if the issue persists. |
| FA 364 | There is a gas valve leak. | Turn off your boiler and contact Worcester Bosch to send out an engineer. |
| FB 365 | This means there is a gas valve leak. | Turn off your boiler and contact Worcester Bosch to send out an engineer. |
| A1 281 | The pump is running with air in the system or stuck. | Reset your boiler but if the issue persists, contact Worcester Bosch for an engineer’s help. |
| EF 349 | The boiler’s operation is at a minimum burner load. | Make sure the system pressure is between 1 and 1.5 bar. If the issue persists, then contact Worcester Bosch. |
| NO CODE 212 | This means the safety or flow temperature is rising too fast. | Reset your boiler but if the error continues then contact Worcester Bosch for an engineer. |
Read more about List Of Ideal Boiler Fault Codes & Error Codes [Solutions]
3. Worcester Bosch CDI Classic Regular Boiler Error Codes
| Fault Code | System Behavior | Solution |
| B1 | Code plug was not detected | If the fault still shows after you’ve pressed ‘reset’, contact Worcester Bosch for a further inspection. |
| C6 | Fan speed is too low | The fan lead and connector need inspection and possibly replacing. Please contact Worcester Bosch for a further inspection. |
| E2 | The central heating (CH) flow negative thermistor coefficient (NTC) sensor is not working properly. | Please contact Worcester Bosch so someone can do a further inspection. |
| E9 | The safety temperature limiter in central heating (CH) flow tripped | If the fault remains after you’ve pressed ‘reset’, contact Worcester Bosch for a further inspection. |
| EA | Flame not detected | You should examine if other gas appliances in your home are working normally, that way you’ll be certain if there is a gas supply in the property. Check if the gas supply is on at the meter, but if the boiler still doesn’t turn on, contact Worcester Bosch. |
| F0 | Internal error | If the fault remains after you’ve pressed ‘reset, contact Worcester Bosch for a further inspection. |
| F7 | Flame detected although the appliance is off | Don’t try to reset your boiler. Contact Worcester Bosch for a further inspection instead. |
| FA | Flame detected after gas shut off | The gas valve needs checking. You won’t be able to fix this problem so please contact Worcester Bosch for a further inspection. |
| FD | The reset button was pressed by mistake | Press the ‘reset’ button again. If the problem continues, contact Worcester Bosch for a further inspection. |
4. Worcester Bosch Greenstar I System / Combi Boiler Error Codes
| Fault Code | System Behavior | Solution |
| 226 | The service tool is connected in the blocking error history menu | Try and reset your boiler, if the error remains, then contact Worcester Bosch for an engineer’s help. |
| FD 231 | The power got interrupted during a lockout | Reset the boiler |
| C7 214 | The fan does not run during the start-up phase – the fan’s harness connector should be checked | Defective fan – call a boiler engineer |
| C6 215 | Fan speed is too high – check the fan harness and connector | Reset the boiler |
| C7 216 | Fan speed is too low – check the fan harness and connector | Reset the boiler |
| C7 217 | The fan has stopped during appliance operation | This isn’t something you’ll be able to fix. Contact Worcester Bosch for an engineer’s help. |
| C1 264 | The fan stopped during operation | Reset the boiler. If the fault remains, call a boiler engineer. |
| C4 273 | Due to continuous fan operation for 24 hours, the appliance is temporarily blocked | It will shut off to protect the fan. |
| E2 222 | The flow temperature sensor has shorted | Call a boiler engineer. |
| E2 233 | The flow temperature sensor is disconnected | Call a boiler engineer. |
| E9 276 | Primary flow temperature exceeded 95°C | Check that the pressure is between 1.0 and 1.5 bar. Try to reset the boiler, but contact Worcester Bosch for an engineer’s help if the issue persists. |
| E2 350 | The flow temperature sensor has shorted | Check that the pressure is between 1.0 and 1.5 bar. Try to reset the boiler but if the issue persists, then contact Worcester Bosch for an engineer’s help. |
| E2 351 | The flow temperature sensor is disconnected | Check that pressure is between 1.0 and 1.5 bar. Try to reset the boiler. If the issue persists, then contact Worcester Bosch for an engineer’s help. |
| FA 306 | Ionisation was detected after the gas valve closed | Try to reset your boiler but if it doesn’t reset then contact Worcester Bosch. |
| EA 227 | No ionisation was detected after ignition | Please contact Worcester Bosch to get an engineer’s help. If you spot a leak, turn off your boiler and contact Worcester Bosch to get the components replaced. |
| F7 228 | Isioniation current detected before burner start | The best course of action is to reset the system, but please contact Worcester Bosch to further inspect if the issue persists. |
| EA 229 | 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 persists, then contact Worcester Bosch for an engineer’s assistance. |
| EA 261 | The heat control module (HCM) is potentially defective – reset the appliance | Reset the boiler but if the issue remains, you will need to call a boiler engineer. |
| 9U 233 | The control box or heat control module (HCM) is either loose or defective, the HCM needs to be checked | This isn’t something you’ll be able to fix. Contact Worcester Bosch for an engineer’s help. |
| C4 237 | The heat control module (HCM) or control box is defective | Call a boiler engineer. |
| F0 238 | The boiler is not registering a flame due to a fault in the gas valve or errors in the control box maybe it is incorrect, or its connection is loose. | Double-check that the system pressure is between 1.0 and 1.5 bar. Also, check whether other gas appliances are working as normal, to confirm that your gas supply is present. If you’ve done this and your boiler still isn’t operating correctly, then contact Worcester Bosch. |
| F0 239 | The control box or the heat control module (HCM) is defective – the control box connections should be checked | This may be an electrical issue, so please contact Worcester Bosch for an engineer’s help. |
| F0 242 | The control box or the heat control module (HCM) is defective – the HCM and control box connections should be checked | This may be an electrical issue, so please contact Worcester Bosch for an engineer’s help. |
| B7 257 | Control box or the heat control module HCM) is defective- the HCM and control box connections should be checked | Please contact Worcester Bosch for a further inspection. |
| F0 258 | Control box or the heat control module (HCM) is defective – HCM or control box connections should be checked | This isn’t something you can fix. Contact Worcester Bosch for an engineer’s assistance. |
| EH 258 | When your boiler displays an EH 258 error code it indicates that the HCM which plays a crucial role in regulating the temperature and ensuring the efficiency is defective– HCM or control box connections should be checked. | This isn’t something you can fix. Contact Worcester Bosch for an engineer’s assistance. This issue is related internally to the boiler meaning that it should not be solved by yourself, and you will have to contact a gas-safe registered engineer and let him inspect the problem. |
| F1 259 | Control box or the heat control module (HCM) is defective – HCM or control box connections should be checked | This isn’t something you can fix. Contact Worcester Bosch for an engineer’s assistance. |
| F0 262 | Control box or the heat control module (HCM) is defective – HCM or control box connections should be checked | Try resetting your boiler. If that doesn’t fix the problem, then the issue might be internally which you will not be able to fix and will have to contact a gas-safe engineer. Also, if you haven’t serviced your boiler for more than 12 months then it is also suggested that you contact an engineer and let him inspect the boiler to spot future issues before they get more complex. |
| F1 263 | The control box or the heat control module (HCM) is defective – Either the HCM has loosened your boiler, or the wrong control box has been installed. | To solve the problem try resetting your boiler if that does not solve the problem then the problem might be complex and cannot be solved by you. For that, you will need to contact a certified professional. Contact Worcester Bosch for an engineer’s assistance. |
| F0 272 | Control box or the heat control module (HCM) is defective – control box and connections need checking or HCM might not be inserted properly and need replacing | This isn’t something you’ll be able to fix. Contact Worcester Bosch for an engineer’s assistance. |
| F0 280 | Control box or the heat control module (HCM) is defective – control box and connections need checking or HCM might not be inserted properly and need replacing | This isn’t something you’ll be able to fix. Contact Worcester Bosch for an engineer’s assistance. |
| F0 290 | Control box or the heat control module (HCM) is defective – control box and connections need checking or HCM might not be inserted properly and need replacing | This isn’t something you’ll be able to fix. Contact Worcester Bosch for an engineer’s assistance. |
| 328 | Control box or the heat control module (HCM) is defective – control box and connections need checking or HCM might not be inserted properly and need replacing | This isn’t something you’ll be able to fix. Contact Worcester Bosch for an engineer’s assistance. |
| 235 | Incompatible heat control module (HCM) software versions – control box needs the latest software | Please contact Worcester Bosch for an engineer’s assistance. |
| 356 | Low mains voltage – the voltage may be interrupted or inconsistent so it should be checked | This may require an electrician if it’s an issue with your house mains |
| 360 | Heat control module (HCM) invalid – the inserted HCM does not correspond with the control box | Please contact Worcester Bosch for an engineer’s assistance. |
| A8 362 | Low mains voltage – the voltage may be interrupted, inconsistent or heat control module (HCM) invalid | This may require an electrician if it’s an issue with your house mains |
| CC 800 | Outdoor sensor defect available when an accessory outdoor sensor is connected | Please contact Worcester Bosch for an engineer’s assistance. |
| A1 281 | Pump stock or running dry | Try to reset your boiler. If the issue persists, contact Worcester Bosch to send out an engineer. |
| E9 224 | Flue or high limit thermostat activated | Try to reset your boiler. If the issue persists then contact Worcester Bosch for a boiler’s assistance. |
| D4 341 | Primary flow temperature rising too fast | This isn’t something you’ll be able to fix. The problem might be related to internal wiring and operation of the pump, trapped air within the system, and problems with circulation within the system. These problems can be best diagnosed and solved by a certified professional, so you must contact Worcester Bosch for an engineer’s assistance. |
5. Worcester Bosch GB162 Boiler Error Codes
| Fault Code | System Behavior | Solution |
| 208 | The boiler is in chimney sweep mode | This isn’t something you’ll be able to fix. Please contact Worcester Bosch for an engineer’s assistance. |
| 200 | The boiler is in heating mode | Please contact Worcester Bosch for an engineer’s assistance. |
| 201 | The boiler is currently in domestic hot water (DHW) mode | Please contact Worcester Bosch for an engineer’s assistance. |
| 202 | The boiler is waiting – there was a heat demand from the modulating or on-off control | Please contact Worcester Bosch for an engineer’s assistance. |
| 203 | The boiler is on standby | Please contact Worcester Bosch for an engineer’s assistance. |
| 204 | The boiler is waiting – the actual temperature is higher than the calculated or selected boiler temperature | Please contact Worcester Bosch for an engineer’s assistance. |
| 212 | The temperature recorded by the safety or flow temperature sensor is rising too rapidly. | Please contact Worcester Bosch for an engineer’s assistance. |
| 226 | The diagnosis tool was connected and is now locked out | Please contact Worcester Bosch for an engineer’s assistance. |
| 260 | The flow temperature sensor doesn’t detect a rise in temperature after a burner start | Please contact Worcester Bosch for an engineer’s assistance. |
| 265 | The boiler is waiting in response to a heat demand – it switches regularly to partial load | Please contact Worcester Bosch for an engineer’s assistance. |
| 268 | Component test phase | Please contact Worcester Bosch for an engineer’s assistance. |
| 270 | The boiler is modulating upwards | Please contact Worcester Bosch for an engineer’s assistance. |
| 283 | The boiler is getting prepared for a burner start – the fan and pump are activated | Please contact Worcester Bosch for an engineer’s assistance. |
| 284 | The gas valve is switched | Please contact Worcester Bosch for an engineer’s assistance. |
| 305 | The boiler is waiting for the domestic hot water (DHW) operation to come to an end | Try to reset the boiler, but contact Worcester Bosch for an engineer’s assistance if the issue persists. |
| 235 | The KIM (boiler identification module) is really new for the burner control unit | Please contact Worcester Bosch for an engineer’s assistance. |
| 360 | The fitted KIM is not compatible with the burner control unit | Please contact Worcester Bosch for an engineer’s assistance. |
| 9A 361 | The fitted burner control unit is not compatible with the KIM (boiler identification module). | Please contact Worcester Bosch for an engineer’s assistance. |
| 9U 233 | The control box or heat control module (HCM) is loose or defective. | Please contact Worcester Bosch for an engineer’s assistance. |
| A3 317 | There is a short circuit in the flue gas temperature sensor contacts | Please contact Worcester Bosch for an engineer’s assistance. |
| B7 257 | The burner control unit or the KIM is defective | Please contact Worcester Bosch for an engineer’s assistance. |
| C1 264 | No power supply or control signal to the fan during operation | Please contact Worcester Bosch for an engineer’s assistance. |
| C4 273 | The boiler was switched off for 2 minutes because it had been operating continuously for over 24 hours | Please contact Worcester Bosch for an engineer’s assistance. |
| C6 215 | Fan speed is too high | Please contact Worcester Bosch for an engineer’s assistance. |
| C6 216 | Fan speed is too low | Please contact Worcester Bosch for an engineer’s assistance. |
| C7 214 | The fan does not run during the start phase | Please contact Worcester Bosch for an engineer’s assistance. |
| C7 217 | When starting up, the fan speed is irregular | Reset the boiler or contact Worcester Bosch for an engineer. |
| CE 207 | Water pressure is too low | Try to top up the pressure so that the needle is between 1 and 1.5 bar. If the pressure continues to drop, contact Worcester Bosch as you may have a leak. |
| CE 266 | Pump test failed | Please contact Worcester Bosch for an engineer’s assistance. |
| D1 240 | The boiler return temperature sensor contacts have short-circuited | Please contact Worcester Bosch for an engineer’s assistance. |
| D1 241 | The boiler return temperature sensor contacts have interrupted | Please contact Worcester Bosch for an engineer’s assistance. |
| D3 232 | The external switching contact has opened | Please contact Worcester Bosch for an engineer’s assistance. |
| D4 213 | The actual temperature recorded by the return or flow temperature sensor is rising too quickly | Please contact Worcester Bosch for an engineer’s assistance. |
| D4 271 | The actual temperature difference between flow and safety temperature sensor is too high | Please contact Worcester Bosch for an engineer’s assistance. |
| D4 286 | The boiler return temperature sensor detected a return temperature higher than 105°c | Please contact Worcester Bosch for an engineer’s assistance. |
| E2 222 | There is a short circuit in the flow temperature sensor contacts | Please contact Worcester Bosch for an engineer’s assistance. |
| E2 223 | The flow temperature sensor contacts have been interrupted | Please contact Worcester Bosch for an engineer’s assistance. |
| E5 218 | The temperature captured by the flow temperature sensor is over 105°C | Please contact Worcester Bosch for an engineer’s assistance. |
| E9 210 | The temperature measured by the flue gas sensor is too high and is open. | Please contact Worcester Bosch for an engineer’s assistance. |
| E9 219 | The safety temperature sensor has captured a temperature over 105°C | Please contact Worcester Bosch for an engineer’s assistance. |
| E9 220 | This means the safety temperature sensor contacts have shorted or the safety temperature sensor has detected a temperature above 130°c. | Please contact Worcester Bosch for an engineer’s assistance. |
| E9 224 | The contacts of the safety temperature sensor have been interrupted | Please contact Worcester Bosch for an engineer’s assistance. |
| E9 276 | That the primary flow temperature is over 95°C. | Please contact Worcester Bosch for an engineer’s assistance. |
| E9 277 | The safety temperature sensor has measured temperature over 95°C | Please contact Worcester Bosch for an engineer’s assistance. |
| E9 285 | the boiler return temperature sensor has measured a temperature higher than 95°c | Please contact Worcester Bosch for an engineer’s assistance. |
| E9 318 | The flue gas temperature sensor contacts are interrupted | Please contact Worcester Bosch for an engineer’s assistance. |
| EA 227 | An insufficient ionisation current was measured following ignition of the burner | Unfortunately, this isn’t something you’ll be able to fix yourself, so please contact Worcester Bosch to send out an engineer. If you spot a leak, turn off your boiler and contact Worcester Bosch to get the components replaced. |
| EA 229 | The ionisation current detected during the burning phase was insufficient | Check the pressure is between 1.0 and 1.5 bar. Try to reset the boiler, if the issue still persists, then contact Worcester Bosch for an engineer’s assistance. |
| EA 234 | The gas valve contacts were interrupted | This isn’t something you’ll be able to fix. Please contact Worcester Bosch for an engineer’s assistance. |
| EA 261 | The burner control unit is faulty | Try to reset the boiler but if the issue remains, then contact Worcester Bosch for an engineer’s assistance. |
| EA 269 | The ignition device has been activated for a long period of time | This isn’t something you’ll be able to fix. Please contact Worcester Bosch for an engineer’s assistance. |
| F0 238 | The burner control unit KIM is defective. | Double-check to ensure the system pressure is between 1.0 and 1.5 bar. Also check any other gas appliances to see if they are working normally, to confirm that your gas supply is present. If you’ve done this and your boiler still won’t operate correctly, then contact Worcester Bosch. |
| F0 239 | The burner control unit KIM (boiler identification module) has an error. Cabling may have poor contact breaks and pinching or the wiring and plug of the burner control unit need checking, along with the operating characteristics of the boiler by replacing the burner control unit. | This may be an electrical issue, so please contact Worcester Bosch for an engineer’s assistance. |
| F0 242 – F0 253, and F0 255, F0 259, F0 263, F0 267, F0 272 | The burner control unit (KIM) is defective – the wiring of the burner control unit needs to be checked, along with the operating characteristics of the boiler by replacing the burner control unit. | This may be an electrical issue, so please contact Worcester Bosch for an engineer’s assistance. |
| F0 278 | The sensor test failed – plug sensors and cabling need to be checked | This isn’t something you’ll be able to fix. Please contact Worcester Bosch for an engineer’s assistance. |
| F0 279 | The burner control unit, or KIM, is faulty – the control unit may need replacing | This isn’t something you’ll be able to fix. Please contact Worcester Bosch for an engineer’s assistance. |
| F0 280 | The burner control unit is faulty | This isn’t something you’ll be able to fix. Contact Worcester Bosch for an engineer’s assistance. |
| F0 287 | The burner control unit, or KIM, has some error | This isn’t something you’ll be able to fix. Please contact Worcester Bosch for an engineer’s assistance. |
| F0 290 | The KIM or burner control unit is defective | Contact Worcester Bosch for an engineer’s assistance. |
| F7 228 | An ionisation current was detected before the burner started | The best thing to do is to try and reset the system, if the issue persists then please contact Worcester Bosch to take a further inspection. |
| F7 328 | A brief power failure has occurred | This isn’t something you’ll be able to fix. Please contact Worcester Bosch for an engineer’s assistance. |
| FA 306 | An ionisation current was measured after the burner shut off | Try to reset your boiler, if it doesn’t reset then contact Worcester Bosch. |
| FD 231 | The mains voltage was interrupted due to an interlocking fault | Try to reset your boiler, but if the code remains, contact an electrician. |
| EC 256 | The burner control unit has an error | This isn’t something you’ll be able to fix. Please contact Worcester Bosch for an engineer’s assistance. |
| EH 258 | The burner control unit is faulty – check the plug and wiring. | This isn’t something you’ll be able to fix. Contact Worcester Bosch for an engineer’s assistance. |
| GB162 | The ignition device has been activated for too long. | This isn’t something you’ll be able to fix. Please contact Worcester Bosch for an engineer’s assistance. |
| H07 | The current water pressure is extremely low which limits the performance in heat mode, along with domestic hot water (DHW) mode | This isn’t something you’ll be able to fix. Please contact Worcester Bosch for an engineer’s assistance. |
| HrE | The boiler keeps resetting | You need to contact an engineer to fix this problem. |
| rE | The boiler resets | Wait for the boiler to reset, if the issue persists – then please contact Worcester Bosch for an engineer’s assistance. |
6. Worcester Bosch Greenstar Ri Boiler Faults Codes
| Fault Code | System Behavior | Solution |
| No light | There is no power at the control board | Try to reset the boiler, but contact Worcester Bosch for an engineer’s assistance if the issue persists. |
| Light on | Appliance on but not operating during demand | Try to reset the boiler, but contact Worcester Bosch for an engineer’s help if the issue remains. |
| Slow flash (mostly off flashes on) | Ignition lockout. | Try to reset your boiler. This can be done by turning the control knob anti-clockwise to reset the position. If this does not fix the problem then contact Worcester Bosch for an engineer’s help. |
| Slow flash (mostly on flashes off) | Flue overheats or heat exchangers overheat. | Try to reset your boiler. This can be done by turning the control knob anti-clockwise to reset the position. If this does not fix the problem then contact Worcester Bosch for an engineer’s help. |
| Fast flash | Volatile lockout sensor fan or code plug | Try to reset your boiler. If this does not fix the problem then contact Worcester Bosch for an engineer’s help. |
| 2 pulses | The check-service mode switch is in minimum position | Try to reset your boiler. If this does not fix the problem then contact Worcester Bosch for an engineer’s help. |
| 5 pulses | The Check-service mode switch is in the max position. | Try to reset your boiler. If this does not fix the problem then contact Worcester Bosch for an engineer’s help. |
7. Worcester Bosch Greenstar 8000 life Combi Boiler Error Codes
| Fault Code | System Behavior | Solution |
| 200 O | The boiler is in heating mode. | Try to reset your boiler. If this does not fix the problem then contact Worcester Bosch for an engineer’s help. |
| 201 O | Boiler in hot water mode. | Try resetting the boiler. This should fix it. |
| 202 O | The boiler is in anti-cycle mode. | Try to reset your boiler. If this does not fix the problem then contact Worcester Bosch for an engineer’s help. |
| 203 0 | This means the boiler is on standby – no heat energy demand. | Try to reset your boiler. If this does not fix the problem then contact Worcester Bosch for an engineer’s help. |
| 204 O | The current primary water temperature is higher than the set value. | Try to reset your boiler. If this does not fix the problem then contact Worcester Bosch for an engineer’s help. |
| 208 O | This shows that the boiler is in chimney sweep demand. | Try to reset your boiler. If this does not fix the problem then contact Worcester Bosch for an engineer’s help. |
| 224 V | The safety temperature limiter has tripped. | Try top-up water until the reset pressure is reached. If the issue persists, then contact Worcester Bosch for an engineer’s help. |
| 227 V | There is no flame signal after the ignition burner. The control unit may need replacing. | Try to reset your boiler. If this does not fix the problem then contact Worcester Bosch for an engineer’s help. |
| 228 V | There is a flame signal without a flame present. The air/gas ratio control valve may need to be replaced. | Try to reset the boiler. If this does not fix the problem then contact Worcester Bosch for an engineer’s help. |
| 305 0 | The boiler is in hot water anti-cycle mode. | Try to reset your boiler. If this does not fix the problem then contact Worcester Bosch for an engineer’s help. |
| 306 V | There is an issue with the flame signal after the fuel supply is closed. The air/gas ratio control valve may need to be replaced. | Try to reset your boiler. If this does not fix the problem then contact Worcester Bosch for an engineer’s help. |
| 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. If this does not fix the problem then contact Worcester Bosch for an engineer’s help. |
| 1010 O | There is no BUS communication cable, EMS-Bus isn’t connected or is damaged – connect the cable for the EMS-Bus or replace the damaged cable exchange fuse. | Try to reset your boiler. If this does not fix the problem then contact Worcester Bosch for an engineer’s help. |
| 1017 W | The water pressure is too low – the water needs topping up and the pressure sensor or vent system could need replacing. | Try topping up your pressure. If this does not fix the problem then contact Worcester Bosch for an engineer’s help. |
| 1021 B | The hot water temperature sensor is faulty – the plug to the hot water temperature sensor may be disconnected.. | Try to reset your boiler. If this does not fix the problem then contact Worcester Bosch for an engineer’s help. |
| 1022 B | The hot water storage temperature sensor does not work. | Try to reset your boiler. If this does not fix the problem then contact Worcester Bosch for an engineer’s help. |
| 1037 W | The outside temperature sensor is not working – check the connecting lead. | Try to reset your boiler. If this does not fix the problem then contact Worcester Bosch for an engineer’s help. |
| 1065 B | The pressure sensor is not connected or defective – check the pressure sensor connection because it may need to be replaced.. | Try to reset your boiler. If this does not fix the problem then contact Worcester Bosch for an engineer’s help. |
| 1068 W | The outside temperature sensor does not work – check the connecting lead. | Try to reset your boiler. If this does not fix the problem then contact Worcester Bosch for an engineer’s help. |
| 1073 W | The temperature sensor may need replacing. | Try to reset your boiler. If this does not fix the problem then contact Worcester Bosch for an engineer’s help. |
| 1074 W | No signal from the flow temperature sensor available – connect the plug to the flow temperature sensor correctly or the temperature sensor might need to be replaced. | Try to reset your boiler. If this does not fix the problem then contact Worcester Bosch for an engineer’s help. |
| 1075 W | Short circuit of the temperature sensor at the heating block – temperature sensor may need replacing. | Try to reset your boiler. If this does not fix the problem then contact Worcester Bosch for an engineer’s help. |
| 1076 W | 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. If this does not fix the problem then contact Worcester Bosch for an engineer’s help. |
| 2920 V | Error with the flame monitoring. | Try to reset your boiler. If this does not fix the problem then contact Worcester Bosch for an engineer’s help. |
| 2924 V | No feedback from the modulating gas valve. The gas valve relay is defective. | Try to reset your boiler. If this does not fix the problem then contact Worcester Bosch for an engineer’s help. |
| 2925 V | Feedback from the modulating gas valve is too low. | Try to reset your boiler. If this does not fix the problem then contact Worcester Bosch for an engineer’s help. |
| 2927 B | The flame failed during the burner operation. | Try to reset your boiler. If this does not fix the problem then contact Worcester Bosch for an engineer’s help. |
| 2946 V | The incorrect code plug has been detected – it needs replacing. | Try to reset your boiler. If this does not fix the problem then contact Worcester Bosch for an engineer’s help. |
| 2948 B | There is no flame signal. If the fault occurs, again and again, the setting of the CO2 valves need to be checked. | Try to reset your boiler. If this does not fix the problem then contact Worcester Bosch for an engineer’s help. |
| 2950 B | There is no flame signal. | Try to reset your boiler. If this does not fix the problem then contact Worcester Bosch for an engineer’s help. |
| 2963 B | The signal from the heat exchanger and the flow temperature sensor is outside of range. | Try to reset your boiler. If this does not fix the problem then contact Worcester Bosch for an engineer’s help. |
| 2964 B | The flow rate in the heat exchanger is too low. | Try to reset your boiler. If this does not fix the problem then contact Worcester Bosch for an engineer’s help. |
| 2965 B | The flow temperature is too high. | Try to reset your boiler. If this does not fix the problem then contact Worcester Bosch for an engineer’s help. |
| 966 B | The flow temperature rise in the heat exchanger is very rapid. | Try to reset your boiler. If this does not fix the problem then contact Worcester Bosch for an engineer’s help. |
| 2967 B | The heat/flow exchanger temperature sensor differential is too great. | Try to reset your boiler. If this does not fix the problem then contact Worcester Bosch for an engineer’s help. |
| 2970 B | The pressure drop in the heating system is too fast. | Try to reset your boiler. If this does not fix the problem then contact Worcester Bosch for an engineer’s help. |
| 2971 B | The system pressure is too low – the heating system needs venting or water needs topping up until the preset pressure is reached. | To fix, replace the cable to the pressure sensor and replace the pressure sensor. Otherwise, try to reset your boiler. If this does not fix the problem then contact Worcester Bosch for an engineer’s help. |
8. Worcester 4000 Error Codes
| Fault Code | System Behavior | Solution |
|---|---|---|
| 1021 | Indicates faulty cylinder charging or hot water temperature sensor. | Turn off the boiler and check for open or short circuit in the hot water sensor. Refit the sensor if it has fallen off the pipe. |
| 224 | Indicates system overheating, causing it to stop operating. | Contact a certified professional or Worcester Bosch for engineer assistance. This may indicate a software or internal issue requiring expert diagnosis and repair. |
What do the error symbols indicate on my Worcester boiler?
Symbol 1: Siphon fill mode:
This error indicates that the boiler hasn’t been used for a day or two due to which the control knob has been turned down and backed up. This is perfectly normal as it is a safety feature of the boiler making the boiler run at a low burn for 15 minutes to fill the condense trap.
All you need to do is wait for 15 minutes as the boiler will be back to normal, if it takes more than 15-30 minutes then contact Worcester Bosch.
Symbol 2: Keylock (Child Lock):
This symbol indicates that the front panel has been locked (This feature is only available in new Greenstar 24/28 only)
Symbol 3: –
This symbol indicates that one key has been pressed.
Symbol 4:
This symbol indicates that two keys have been pressed at once.
Symbol 5:
This symbol indicates that the boiler is operating in maximum mode. All you need to do is leave the boiler alone for 15 minutes and will be back to normal.
If the problem persists let’s say more than 15 minutes and up to 30 minutes, then contact Worcester Bosch for assistance.
Symbol 6:
This symbol means that the boiler is operating within a set range (service function 1A).
Symbol 7:
This means the boiler is operating in minimum mode. And it should not last longer than 15 minutes if it does then contact Worcester Bosch for assistance.
Symbol 8:
This symbol indicates air purge mode, meaning the boiler will not fire up instead it will pulse the pump on and off. This happens mainly due to when the boiler is first switched on or if a circuit board is changed.
This air purge mode will also last 15 minutes in your boiler and will then return to its normal operation if it’s not then contact Worcester Bosch for assistance.
Symbol 9:
This symbol is known as the save function it is only displayed on the screen when adjustments are made in the menu.
Symbol 10:
This symbol indicates temperature blocking mode also known as gradient limitation. This happens when the boiler is programmed to increase its flow temperature by a certain rate “degrees” and it exceeds that rate. Due to this, the symbol appears on the screen and the burner stops functioning for a few minutes and then restarts afterwards.
This is an indication that the temperature is increasing quickly not necessarily overheating but can mean issues with the circulation. If the system does not reset and the issues persist either contact a certified gas-safe engineer or contact Worcester Bosch for assistance.
Symbol 11:
When this symbol arises, the display will flash between this symbol and the flow temperature indicating that the service is due, so get serviced immediately to prevent the chances of breakdown.
Symbol 12:
When this symbol arises the display flashes between the symbols indicating that the heating circuit pump is blocked. Either contact a certified engineer or contact Worcester Bosch.
Symbol 13:
This is an SE code which is not an error code but indicates that the boiler has been operating for 2324 hours which is accumulative to 12-month periods and due a service. Arrange a boiler service right away.
Frequently Asked Questions (FAQs)
Why is my Worcester Boiler Flashing?
There are three kinds of lights on the Worcester boiler and each one indicates something different. The green light, for instance, typically indicates that the burner is operating properly, which means it is a good sign. However, sometimes even with the boiler working fine, the green light can go off. There are reasons for this, for instance, LED or PCB failure, mainly the things that power the light on the boiler’s panel.
The blue light indicates that the boiler has power going to it. There may be reasons why the blue light is not showing; for instance, LED and PCB failure. Additionally, it could also point to socket failure – it is worth checking a few of the appliances with the same socket the boiler is usually plugged into in the house and see if they are working okay.
Why is my Boiler Flashing EA?
The EA fault code indicates the need for activation of a safety device to prevent any gas from being let out when the boiler has failed to light.
What does U2 mean on a Worcester Boiler?
This code means that the boiler flow temperature is too high and the boiler will shut down until it has cooled down.
What does the Worcester Bosch fault code U9 mean?
U9 means the temperature is 109 degrees as measured inside the boiler. The boiler has massively overheated. This is either due to a faulty pump not working, a restriction in the plate heat exchanger or a faulty PCB not sending power to the pump.
What does the fault code h09 means on my Worcester Bosch boiler?
H09 fault code on your Worcester boiler means that your boiler is providing no heating and hot water caused by a communication problem between the pump and the printed circuit board. To solve this problem try resetting your boiler as the problem might be due to a glitch.
If this does not solve the issue, then the problem might be related to the central heating pump and PCB which unfortunately cannot be solved by yourself and will require the expertise of a gas-safe engineer who will inspect the pump and PCB. Contact Worcester Bosch for an engineer’s help.
What does A22 Fault Code mean on Worcester Bosch boiler?
If your Worcester boiler displays an A22 Fault Code, this indicates a loss of RF signal due to incorrect positioning of the room thermostat. To solve the problem, check the signal strength and try repositioning the room thermostat to get better signals. If the boiler is in a loft garage, try wiring the receiver to a wall plate.
What does 6A fault code means on Worcester Bosch boiler?
Fault code 6a on your Worcester Boiler indicates that the safety fuse has run out. This happens mainly due to tampering within the system, or poor maintenance. Also, poor, or loose wiring can be another issue that causes damage. As it is an internal issue to solve the problem you will need to contact a certified gas-safe engineer.
After inspecting the severity of the problem through procedural testing the professional will then recommend you necessary solutions. Although it is recommended that you contact Worcester Bosch for an engineer’s assistance as they will have service performed on an annual basis so that errors like 6a can be potentially avoided in the future.
Posted by: Martin Astley 06 September 2021
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