Worcester Boiler Error Codes: Complete Fault Code List and Solutions
Worcester Bosch boiler fault codes are your boiler’s way of indicating what has gone wrong. Most codes mean the boiler has shut down safely to protect itself. Some can be cleared with a reset others need a Gas Safe engineer.
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), especially when dealing with Worcester boiler problems.
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
| A1 | A7 | A8 | B1 | C6 | E2 |
| E9 | EA | F0 | F7 | FA | FD |
2. Worcester Bosch CDI Compact / Greenstar 27/30 I System / Greenstar 25/30 SI Combi Boiler Error Codes
| T1 | T2 | T3 | T4 | T6 | 9A-362 | C6-215 |
| EA-227 | F7 228 | FB 364 | FB 365 | A1 281 | EF 349 | NO CODE 212 |
3. Worcester Bosch CDI Classic Regular Boiler Error Codes
| B1 | C6 | E2 | E9 | EA | F0 | F7 | FA | FD |
4. Worcester Bosch Greenstar I System / Combi Boiler Error Codes
5. Worcester Bosch GB162 Boiler Error Codes
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 | Low Boiler Pressure (Repressuring required) |
7. Worcester Bosch Greenstar 8000 life Combi Boiler Error Codes
8. Worcester 4000 Error Codes
Each of the fault codes listed above is explained in detail in the sections below, covering what the code means and the steps you should take to resolve it. Use the section that matches your specific Worcester Bosch boiler model to find the most accurate guidance.
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 Worcester Bosch boiler 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. In some scenarios, checking the Worcester boiler display symbols can help confirm the issue before contacting the support. |
| F0 | Internal error within the boiler system. | Reset the boiler. If fault persists, call a Gas Safe engineer. |
| F7 | A flame has been detected, although the appliance is not on. | Don’t be tempted to reset your Worcester 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 | No flame detected; possible gas valve fault, blocked condensate, damaged ignition lead, or internal leak. | Turn off the boiler if you spot a leak. Call a Gas Safe engineer to diagnose and repair. |
| 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 your Worcester Boiler’s Fault code persists 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 | Check gas supply is on at the meter and other gas appliances are working. If the boiler still won’t fire, call a Gas Safe engineer. |
| 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 | No action needed. The boiler shuts off automatically for 2 minutes to protect the fan and restarts on its own. |
| 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 | Ionisation 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. | Call a Gas Safe engineer to inspect and replace the HCM or control box. |
| 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 HCM is defective, check HCM and control box connections. | Check the HCM and control box connections are secure. Reset the boiler. If fault persists, a Gas Safe engineer needs to inspect or replace the HCM or control box. |
| 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. | Check the HCM is properly seated and the correct control box is installed. Reset the boiler. If fault persists, a Gas Safe engineer needs to inspect or replace the control box. |
| 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 | Check for trapped air and bleed the system. Check system pressure is between 1 and 1.5 bar. If fault persists, a Gas Safe engineer needs to inspect the pump and circulation. |
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 | Status code only. No action needed. |
| 201 | Boiler is in hot water mode. | Status code only. No action needed. |
| 202 | Boiler is waiting for a heat demand. | Status code only. No action needed. |
| 203 | The boiler is on standby | Status code only. No action needed. |
| 204 | Boiler is waiting; current temperature is higher than the set temperature. | Status code only. No action needed. |
| 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. |
| Low Boiler Pressure (Repressuring required) | Boiler has stopped operating due to low system pressure. | Top up system pressure to between 1 and 1.5 bar using the filling loop. If pressure keeps dropping, call a Gas Safe engineer as there may be a leak. |
7. Worcester Bosch Greenstar 8000 life Combi Boiler Error Codes
1071 W Return temperature sensor signal out of range.Call a Gas Safe engineer to check connections and replace the sensor if needed. 1072 W Flow temperature sensor faultCall a Gas Safe engineer to inspect the sensor and wiring.
| Fault Code | System Behavior | Solution |
|---|---|---|
| 200 O | The boiler is in heating mode. | Status code only. Boiler is in heating mode. No action needed. |
| 201 O | Boiler in hot water mode. | Status code only. Boiler is in heating mode. No action needed. |
| 202 O | The boiler is in anti-cycle mode. | Status code only. Boiler is in heating mode. No action needed. |
| 203 0 | This means the boiler is on standby – no heat energy demand. | Status code only. Boiler is in heating mode. No action needed. |
| 204 O | The current primary water temperature is higher than the set value. | Status code only. Boiler is in heating mode. No action needed. |
| 208 O | This shows that the boiler is in chimney sweep demand. | Status code only. Boiler is in heating mode. No action needed. |
| 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. | Status code only. Boiler is in heating mode. No action needed. |
| 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 | EMS-Bus cable disconnected or damaged. | Check EMS-Bus cable connection. Replace if damaged. Call a Gas Safe engineer if fault persists. |
| 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. |
| 1070 W | Return temperature sensor fault. | Call a Gas Safe engineer to inspect and replace the return temperature sensor. |
| 1071 W | Return temperature sensor signal out of range. | Call a Gas Safe engineer to check connections and replace the sensor if needed. |
| 1072 W | Flow temperature sensor fault. | Call a Gas Safe engineer to inspect the sensor and wiring. |
| 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 |
|---|---|---|
| 224 B | 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. |
| 232 B | External switching contact has opened, boiler has stopped | Check external wiring connections. If nothing is connected to the switching contact, call a Gas Safe engineer. |
| 281 B | Pump is stuck or running dry due to air in the system. | Check water pressure and bleed air from the system. If pump is seized, a Gas Safe engineer must replace it. |
| 2927 B | Flame failed during burner operation, no ionisation detected. | Check gas supply and pressure. Check flame sense electrode and lead. If fault persists, call a Gas Safe engineer. |
| 2948 B | No flame signal at low output, often caused by wind affecting the flue. | Check CO2 settings and flue terminal position. Call a Gas Safe engineer if fault persists. |
| 2949 B | No flame signal during burner operation. | Reset the boiler. If fault returns, call a Gas Safe engineer to check the gas valve and ignition. |
| 2950 B | No flame signal detected. | Reset the boiler. If fault persists, a Gas Safe engineer must inspect the ignition system and gas valve. |
| 2963 B | Heat exchanger flow temperature sensor signal is out of range. | Call a Gas Safe engineer to check the flow temperature sensor and connections. |
| 2964 B | Flow rate through the heat exchanger is too low. | Check system pressure and bleed any air. If flow rate remains low, call a Gas Safe engineer to inspect the pump and circulation. |
| 2965 B | Flow temperature too high boiler has shut down to protect itself. | Check pressure is between 1 and 1.5 bar. Call a Gas Safe engineer if fault returns after reset. |
| 2966 B | Flow temperature rising too rapidly in the heat exchanger. | Check for airlocks and system pressure. Call a Gas Safe engineer this can indicate a circulation problem. |
| 2967 B | Temperature difference between heat exchanger sensor and flow sensor is too large. | Call a Gas Safe engineer to inspect both sensors and the heat exchanger. |
| 2970 B | System pressure dropping too quickly, possible leak. | Check pipework and radiators for leaks. Top up pressure to 1–1.5 bar. Call a Gas Safe engineer to locate the leak. |
| 2971 B | System pressure too low boiler has stopped. | Top up pressure to 1–1.5 bar. If pressure keeps dropping, call a Gas Safe engineer as there may be a leak. |
| 1010 W | No EMS-Bus communication, cable may be disconnected or damaged. | Check EMS-Bus cable connection. Replace if damaged. Call a Gas Safe engineer if fault persists. |
| 1013 W | Cylinder temperature sensor reading is out of range. | Call a Gas Safe engineer to check and replace the cylinder temperature sensor. |
| 1017 W | System water pressure too low. | Top up pressure to 1–1.5 bar. If pressure keeps dropping, call a Gas Safe engineer there may be a leak or faulty pressure sensor. |
| 1018 W | Pressure sensor reading unusually high pressure. | Call a Gas Safe engineer to inspect the pressure sensor and expansion vessel. |
| 1019 W | Pressure sensor signal out of range. | Call a Gas Safe engineer to check and replace the pressure sensor. |
| 1021W | 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. |
| 1023 W | Hot water temperature sensor reading is out of range. | Call a Gas Safe engineer to inspect the hot water sensor and connections. |
| 1037 W | Outside temperature sensors not working connecting leads may be faulty. | Check the connecting lead. Replace sensor or lead if damaged. Call a Gas Safe engineer if unsure. |
| 1065 W | Pressure sensor not connected or defective. | Check pressure sensor connection. If faulty, a Gas Safe engineer must replace it. |
| 1068 W | Outside temperature sensor not working. | Check the connecting lead. Call a Gas Safe engineer to replace the sensor if faulty. |
| 1070 W | Return temperature sensor fault. | Call a Gas Safe engineer to inspect and replace the return temperature sensor. |
| 1071 W | Return temperature sensor signal out of range. | Call a Gas Safe engineer to check connections and replace the sensor if needed. |
| 1072 W | Flow temperature sensor fault. | Call a Gas Safe engineer to inspect the sensor and wiring. |
| 1073 W | Temperature sensor signal out of range sensor may need replacing. | Call a Gas Safe engineer to check and replace the temperature sensor. |
| 1074 W | No signal from flow temperature sensor plug may be disconnected. | Check the plug connection on the flow temperature sensor. If no signal, call a Gas Safe engineer to replace the sensor. |
| 1075 W | Short circuit in the temperature sensor at the heating block. | Call a Gas Safe engineer to replace the temperature sensor. |
| 1076 W | No signal from the temperature sensor at the heating block | Call a Gas Safe engineer to replace the sensor, connecting lead, or control unit as needed. |
Most Common Worcester Boiler Fault Codes and What They Mean
Worcester boilers display fault codes to tell you exactly what has gone wrong. While the full list varies by model, certain codes appear more often than others. The following codes are the ones Worcester boiler owners encounter most frequently here is what each one means and what to do next.
What Does U9 Mean on a Worcester Boiler?
U9 means the temperature inside the boiler has hit 109°C. The boiler has overheated usually due to a faulty pump, a blocked plate heat exchanger, or a faulty PCB not powering the pump. Do not reset repeatedly. Call a Gas Safe engineer to find the cause.
What Does F0 263 Mean on a Worcester Boiler?
F0 263 means the control box or heat control module (HCM) is defective. Check the HCM is properly seated and all connections are secure. Reset the boiler. If the fault comes back, a Gas Safe engineer needs to inspect or replace the HCM or control box.
What Does FD Mean on a Worcester Boiler?
FD codes on a Worcester boiler indicate an interruption to the mains voltage or a lockout fault. The most common is FD 231 which appears when power was cut during a lockout. In most cases pressing reset clears the code. If FD keeps returning, it points to a wiring issue or repeated lockouts that need a Gas Safe engineer to investigate.
What Does HH Mean on a Worcester Boiler?
HH appears when the heat exchanger has overheated. The boiler will restart on its own once it cools down. If HH keeps coming back, it usually points to low water pressure, a blocked heat exchanger, or a circulation problem. Call a Gas Safe engineer if it recurs.
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: Pressed Key
This symbol indicates that one key has been pressed.
Symbol 4: Two Key Pressed
This symbol indicates that two keys have been pressed at once.
Symbol 5: Maximum Mode
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: Set Range
This symbol means that the boiler is operating within a set range (service function 1A).
Symbol 7: Minimum Mode
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: Air Purge
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: Save Function
This symbol is known as the save function it is only displayed on the screen when adjustments are made in the menu.
Symbol 10: Temperature Blocking Mode
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: Service Due
When this symbol arises, the display will flash between this symbol and the flow temperature indicating that the service is due. Book an annual boiler service immediately to prevent a breakdown.
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Symbol 12: Pump Blocked
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: SE Code
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.
Is Your Worcester Boiler Flashing Blue Light?
If your Worcester Boiler is flashing a blue light, it means a fault in the system. This blue light flashing issue is usually linked with low water pressure, sensor fault or ignition problems. To get this issue resolved, get your boiler professionally inspected by a gas safe engineer followed by the relevant repair procedures for your boiler. If your boiler is older and repeatedly showing faults, it may be worth considering a new boiler instead of continuing to spend on repairs.
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No Hot Water Coming Through My Worcester Boiler
Are you facing a no hot water issue with your Worcester boiler? This issue can be caused by a variety of factors, including a problem with your diverter valve, low system pressure, or even a thermostat problem. Resetting the boiler can temporarily solve this problem but repeated no hot water faults indicate an internal component problem and require a professional boiler repair rather than a simple reset.
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Conclusion
Worcester Bosch boiler fault codes exist to protect your boiler and flag problems early. Some can be cleared with a simple reset others need a Gas Safe engineer straight away. If your boiler is showing a fault code right now, don’t ignore it. A small fault left unattended can turn into a costly repair or a full breakdown. At 24|7 Home Rescue, we help thousands of homeowners get their boilers fixed and protected, whether that’s a one-off repair, annual boiler service or year-round boiler cover.
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Frequently Asked Questions (FAQs)
What do Worcester boiler error codes mean?
Worcester boiler error codes are fault codes that are shown on your boiler when any issue is detected. Every problem has a designated code, from low pressure, faults on pressure sensors, to ignition problems and overheating. The code will inform you what the boiler has detected, and if it has turned off to put itself into a safe condition. Some codes can be cleared easily with a reset, while others will require a Gas Safe engineer. Please check the code before attempting a reset.
Why is my Boiler Flashing EA?
EA is when the boiler cannot ignite and a safety device has activated to prevent gas leakage. Inspect other gas equipment to ensure that the gas is turned on. If gas does not have any issue, reset the boiler. If EA returns, call a Gas Safe engineer to inspect the gas valve, ignition electrode and the condensate pipe.
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 is a communication issue between the pump and the PCB, which results in the boiler system to cease heating and hot water. Reset the boiler first as it may be a glitch. If fault persists, contact a Gas Safe engineer for the pump and PCB to be inspected.
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?
6A means the safety fuse has blown, this is normally due to tampering or poor maintenance or loose wiring within the boiler. You will not be able to correct this yourself, it’s an internal fault. Contact a Gas Safe engineer to install and replace the fuse, and to check wiring.
What does HH mean on a Worcester Bosch boiler?
If the heat exchanger is over heated, HH will be shown. When the boiler cool down, it will start up automatically. When HH recurs, it is typically indicative of low water pressure, clogged heat exchanger or circulation issue. If it happens frequently, please call Gas Safe.
What does F0 263 mean on a Worcester Bosch boiler?
F0 263 indicates that the control box or heat control module (HCM) has a fault. Verify that HCM is in correct position and all connections are secure. Reset the boiler. If the fault is repeated, a Gas Safe engineer will be required to check or repair the HCM or control box.
Is it safe to reset my Worcester Bosch boiler?
Most fault codes can be reset without risk, which clears the temporary glitches and restarts the boiler. Do not reset repeatedly if the same fault is reoccurring; as this can mask a bigger problem. Do not reset if gas leak is detected or if you hear abnormal noises from the boiler. In those cases turn the boiler off and call a Gas Safe engineer immediately.
Is a fault code on my Worcester boiler dangerous?
Most fault codes are not dangerous, they are the boiler’s way of flagging a problem and shutting down safely. But there are some codes that require immediate attention. If your boiler is displaying a gas or flame fault code, e.g. EA, F7 or FA, shut off the boiler and contact a Gas Safe engineer. If gas is detected at any time, do not reset the boiler, leave the premises and call on the National Gas Emergency number 0800 111 999.
At 24|7 Home Rescue, we aim to keep our blogs accurate and helpful at the time of publication. However, details such as images, services, or product information may change. Content is for general information only and not professional advice. For the latest updates, please review our Terms & Conditions or contact us directly. 24|7 Home Rescue accepts no liability for actions based on outdated or incomplete content. Our team is always happy to help with any questions.
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