Worcester boiler error codes and how to fix them
Worcester Bosch Greenstar is our most visited boiler breakdowns and are not a very good boiler in our opinion considering the money that is spent on them.
If your Worcester Bosch boiler is broken we can offer a fixed price to fix it
Worcester Bosch boilers display error codes so depending what the error is we can diagnose what the problem is and fix it for you.
You can always book a boiler service with ourselves which can help prevent problems occuring with your boiler. Most problems that we go out to is because people do not get their boiler serviced
Worcester Bosch problems
There is a lot of issues that can happen with your Worcester
What are Worcester boiler error codes?
The Worcester Bosch error codes will tell you what is wrong with your boiler. Depending what the error code is you can fix it yourself or you will need to get a gas safe engineer to fix it for you.
Some of the errors you will be able to clear yourself but a lot of them you will need the help of our team to diagnose the issues and get them fixed
Worcester bosch when no error codes are given
You can press the spanner button and this acan normally rfesolve the issue but mif it returns to the same fault you will need to give ourselves a ring to sort the problem out
Worcester bosch error codes
If you press the reset button and your boiler is still not working this is normally when tghe blue light flashes fast or slow and this can tell us what the problem is
Worcester Bosch Fault error
There are a number of error codes so lets see how you go about sorting them
Error number?
So it starts with an E follwed by a sequence of numbers and this will determine what is wrong with your boiler
Worcester Bosch maintenance mode
The maintenance mode is easily is like a set of rugby posts back to front and is also when the boiler has been reset and can last for 5 mins before starting properly.
How to reset a Worcester boiler?
Resetting your Worcester boiler is normally a warning sign that something isn’t right with the boiler, If you are having to reset the boiler more often than usual you need to give us a call to find out what the problem is. Give us a call and we can send out a Gas Safe engineer.
Resetting your Worcester Bosch boiler after a fault code
Press the reset button for 3 seconds or more and the boiler should try and go through it’s start up procedure.
Before we send an engineer make sure you try to reset the boiler yourself to see if it’s nothing major that needs fixing. If it’s displaying an error code please tell us when you phone up for an engineer
Worcester boiler EA error code with flashing blue light
If your Worcester boiler is displaying an EA error code it will be follwed by 3 numbers depending on these numbers will determine what’s up with your boiler . Most Worcester boilers come with a guarantee but if it’s not then you can give us a call and we will send a gas safe engineer to look at it.
A21 error for faulty thermostat
The Worcester boiler error code A21 means that your thermostat and boiler are not communicating due to a lack of an RF signal. The most common error is A21 and it can be easily fixed without the help of an engineer.
EA 227 – Blocked or frozen condensate pipe
If you are seeing an EA 227 error code and it is freezing outside you have a frozen condensate pipe. Pour boiling water over the pipe and this should resolve the problem.
C6 error
Another unfortunatley popular err is the Worcester C6 fault code which relates to the fan not working properly – Easily fixed but very annoying and can also be linked to frozen condensate pipes too.
Worcester Bosch error codes & what they mean
There are several different reasons why your boiler is displaying the EA error code. There could be no gas supply to the boiler, another common problem is the electrodes arn’t working or the flame sensor. If you are resetting your boiler a lot this is normally the fault.
What do the Worcester boiler symbols look like?
If your Worcester boiler isn’t working, then there may be some form of symbol displayed on your boiler. Depending on which model you have will depend on which Worcester boiler symbols are showing.
The best way to check is to look at the Worcester manuals either physically or online. Our fault code tables below are probably a quicker way of diagnosing what is wrong with your boiler though and checking if you need a Gas Safe engineer.
Worcester Greenstar 8000 error codes
This includes the Greenstar 8000 Life & Style Combi boiler, Greenstar 8000 Life System boiler, Greenstar 8000 Style System, and the Greenstar 8000 Life Regular boiler.
| Fault Code | Problem description |
| 200 O | Boiler in heating mode |
| 201 O | Boiler in hot water mode |
| 202 O | Boiler in anti-cycle mode |
| 203 0 | Boiler on standby – no heat energy demand |
| 204 O | Current primary water temperature higher than the set value |
| 208 0 | Chimney sweep demand |
| 224 V | Safety temperature limiter has tripped – top-up water until the reset pressure is reached |
| 227 V | No flame signal after ignition – burner control unit could need replacing |
| 228 V | Flame signal without flame present – air/gas ratio control valve or ionisation cable may need replacing |
| 305 0 | Boiler in hot water anti-cycle mode |
| 306 V | Flame signal after closing the fuel supply – the air/gas ratio control valve might need replacing |
| 360 V | Incompatible code plug – check if a correct code plug is installed and exchange or reconnect code plug |
| 815 W/B | Low loss header temperature sensor faulty – check the sensor port or check the differential sensor for incorrect installation position or breakage |
| 1010 O | No BUS communication cable, EMS-Bus isn’t connected or damaged – connect the cable for the EMS-Bus or replace the damaged cable exchange fuse |
| 1017 W | Water pressure too low – the water needs topping up and the vent system or pressure sensor may need replacing |
| 1021 B | The hot water temperature sensor is defective – the plug to the hot water temperature sensor may not be connected |
| 1022 B | Hot water storage temperature sensor is defective – connect the plug to the hot water temperature sensor correctly, mount the hot water temperature sensor correctly or replace the hot water temperature sensor |
| 1037 W | The outside temperature sensor is defective – check the connecting lead |
| 1065 B | Pressure sensor defective or not connected – check pressure sensor connection as it may need replacing |
| 1068 W | Outside temperature sensor defective – check the connecting lead |
| 1073 W | Short circuit of the flow temperature sensor – the temperature sensor may need replacing |
| 1074 W | No signal from the flow temperature sensor available – connect the plug to the flow temperature sensor correctly or temperature sensor could need replacing |
| 1075 W | Short circuit of the temperature sensor at the heating block – temperature sensor may need replacing |
| 1076 W | No signal from the temperature sensor at the heating block available – replace the temperature sensor, the connecting lead, or the control unit |
| 2920 V | Error with the flame monitoring |
| 2924 V | No feedback from the modulating gas valve. The gas valve relay is defective – press the reset button and apply burner start, wait to see if fault reoccurs, if it does the gas valve needs replacing |
| 2925 V | Feedback from the modulating gas valve is too low |
| 2927 B | Flame failed during burner operation. Open the main shut off valve, shut down the appliance and check the gas line, replace the ionisation electrode, set burner correctly and minimum rated load, check the integrity flue system and if the interconnected room air supply is too small, or the size of the ventilation opening is too small, clean the heating block on the flue gas side or replace the control unit/burner control unit |
| 2946 V | Incorrect code plug detected – the code plug needs replacing |
| 2948 B | No flame signal. With low output, the burner starts automatically after cleaning. If the fault occurs repeatedly, the setting of the CO2 valves need checking |
| 2950 B | No flame signal. Following starting the procedure the burner starts automatically. After cleaning set the correct gas/air ratio correctly |
| 2963 B | The signal from the flow and heat exchanger temperature sensor is outside the permissible range – the connecting lead needs to connect correctly |
| 2964 B | The flow rate in the heat exchanger is too low |
| 2965 B | The flow temperature is too high |
| 2966 B | Flow temperature rise in heat exchanger is too rapid |
| 2967 B | Flow/heat exchanger temperature sensor differential is too great |
| 2970 B | Pressure drop in the heating system is too rapid |
| 2971 B | System pressure is too low – the heating system needs venting or water needs topping up until the preset pressure is reached. Replace the cable to the pressure sensor replace the pressure sensor |
Worcester 4000 error codes
Brand new Worcester 4000 error codes, thee are easily read on their new LCD colour screen.
| Fault Code | Description |
| 1021 | Cylinder charging or hot water temperature sensor faulty. Turn the appliance off and back on again. The hot water sensor has been changed if an open or short circuit or refitted to the pipe if it has fallen off. |
| 224 | Software issue. Arrange a visit from a Worcester Bosch engineer to reset the boiler/PCB. |
Greenstar CDi Highflow error codes
| Fault Code | Description |
| A1 | Pump is dry or running with air in the system – check system pressure |
| A5 | Tank negative thermistor coefficient (NTC) defect |
| A7 | Domestic hot water (DHW) negative thermistor coefficient (NTC) defect |
| A8 | Energy Management System (EMS) communication error |
| B1 | Code plug not detected |
| B2, B3, B4, B5, B6 | Data error |
| B7 | Burner control error |
| C6 | Fan defect |
| D3 | External temperature limiter |
| D5 | Condensate pump failure |
| D6 | Internal heat bank overflow |
| EA | Flame not detected – contact a Gas Safe engineer |
| E2 | Primary negative thermistor coefficient (NTC) defect |
| E9 | Safety temperature limiter in central heating (CH) flow stat tripped |
| F0 | Internal error |
| F1 | ROM fault |
| F7 | Flame detected after the appliance has been shut off |
| FA | Flame detected after gas shut off |
| FD | Reset button pressed – try pressing the reset button again |
Greenstar CDi Compact error codes
| Fault Code | Description |
| T1 | Ignition test – checking the igniter spark |
| T2 | Fan test – checking the basic fan |
| T3 | Pump test – checking the basic pump |
| T4 | Three-way valve test |
| T6 | Ionisation oscillator test |
| 9A 362 | Error – incorrect HCM fitted |
| 9U 233 | Heat Control Module (HCM) error – problem with code plug |
| B7 257 | Internal error – possible control board problem |
| C6 215 | Fan problem – fan is running too fast |
| C7 214 | Fan problem – fan is not running |
| D1 240 | Return sensor error – sensor may be wet or damaged |
| E2 222 | Flow sensor short circuit error |
| E5 218 | Flow temperature is too high |
| E9 219 | Safety sensor fault – temperature is too high, sensor short circuit or open circuit |
| EA 227 | No flame detected or flame signal loss during operation-contact a Gas Safe engineer – Possible blockage (frozen condensate pipe) |
| F0 237 | Internal error |
| F7 228 | Flame error – false flame or flame detected before burner started |
| FA 306 | False flame fault – flame detected after the burner has stopped |
| FD 231 | Mains power fault – electrical power interruption |
| FA 364 | Gas valve EV2 leak test failed – gas valve leak |
| FB 365 | Gas valve EV1 leak test failed |
| A1 281 | Pump stuck or running with air in the system |
| C1 264 | Airflow stopped during the operation |
| C4 273 | Airflow present during last 24 hours |
| D1 240 | Return sensor short circuit |
| D4 271 | The temperature difference between flow and safety sensor exceeds the limit |
| E9 224 | Max thermostat activated – flue gas thermostat overheat |
| EA 227 | No ionisation is detected after ignition (Check frozen condensate pipe) |
| EF 349 | Central heating boil detected – boiler operating at minimum burner load with temperature difference greater than 18°C between Flow & Return. |
| NO CODE 212 | Safety or flow temperature is rising too fast |
Greenstar CDi Classic Regular error codes
| Fault Code | Description |
| B1 | Code plug not detected |
| C6 | Fan speed too low |
| E2 | Central heating (CH) flow negative thermistor coefficient (NTC) sensor defective |
| E9 | Safety temperature limiter in central heating (CH) flow has tripped |
| EA | Flame not detected -contact a Gas Safe engineer |
| F0 | Internal error |
| F7 | Flame detected even though appliance is switched off |
| FA | Flame detected after gas shut off |
| FD | The reset button pressed by mistake |
Greenstar CDi Fi Regular error codes
| Fault code | Description |
| b1 | Code plug is not detected |
| C6 | Fan speed is too low |
| E9 | Safety temperature limiter in CH flow has tripped |
| EA | Flame not detected – contact a Gas Safe engineer |
| F0 | Internal error |
| F7 | Flame detected even though the boiler is switched off |
| FA | Flame detected after gas shut off |
| FD | The reset button pressed by mistake |
Greenstar i System 27/30 error codes
| Fault Code | Description |
| T1 | Ignition test – checking the igniter spark |
| T2 | Fan test – checking the basic fan |
| T3 | Pump test – checking the basic pump |
| T4 | Three-way valve test |
| T6 | Ionisation oscillator test |
| 9A 362 | Error – incorrect HCM fitted |
| 9U 233 | Heat Control Module (HCM) error – problem with code plug |
| B7 257 | Internal error – possible control board problem |
| C6 215 | Fan problem – fan running too fast |
| C7 214 | Fan problem – fan not running |
| D1 240 | Return sensor error – sensor may be wet or damaged |
| E2 222 | Flow sensor short circuit error |
| E5 218 | Flow temperature too high |
| E9 219 | Safety sensor fault – temperature too high, sensor short circuit or open circuit |
| EA 227 | No flame detected or flame signal loss during operation (check frozen condensate pipe) |
| F0 237 | Internal error |
| F7 228 | Flame error – false flame or flame detected before burner started |
| FA 306 | False flame fault – flame detected after the burner stopped |
| FD 231 | Mains power fault – electrical power interruption |
| FA 364 | Gas valve EV2 leak test failed – gas valve leak |
| FB 365 | Gas valve EV1 leak test failed |
| A1 281 | Pump stuck or running with air in the system |
| C1 264 | Airflow stopped during the operation |
| C4 273 | Airflow present during last 24 hours |
| D1 240 | Return sensor short circuit |
| D4 271 | The temperature difference between flow and safety sensor exceeds the limit |
| E9 224 | Max thermostat activated – flue gas thermostat overheat |
| EA 227 | No ionisation detected after ignition ( Check frozen condensate pipe) |
| EF 349 | Central heating boil detected – boiler operating at minimum burner load with temperature difference greater than 18°C between Flow & Return. |
| NO CODE 212 | Safety or flow temperature rising too fast |
Greenstar i Combi and System 9/24 boiler error codes
| Fault Code | Description |
| 226 | The service tool has been connected in the blocking error history menu |
| FD 231 | The power has been interrupted during a lockout |
| C7 214 | The fan does not run during the start-up phase – the fan harness connector needs checking |
| C6 215 | Fan speed too high – check the fan harness and connector |
| C7 216 | Fan speed too low – check the fan harness and connector |
| C7 217 | The fan has stopped during appliance operation |
| C1 264 | The fan stopped during the operation |
| C4 273 | Continuous fan operation for the last 24 hours – appliance temporarily blocked |
| E2 222 | Flow temperature sensor shorted |
| E2 233 | Flow temperature sensor disconnected |
| E9 276 | Primary flow temperature exceeded 95°c |
| E2 350 | Flow temperature sensor shorted |
| E2 351 | Flow temperature sensor disconnected |
| FA 306 | Ionisation detected after the gas valve closed |
| EA 227 | No ionisation detected after ignition – Can be caused by frozen condensate pipe |
| F7 228 | Ionisation current detected before burner start |
| EA 229 | Loss of ionisation signal during operation |
| EA 261 | Heat control module (HCM) potentially defective – reset the appliance |
| 9U 233 | The control box or heat control module (HCM) is defective or loose, the HCM needs to be checked |
| C4 237 | The control box or heat control module (HCM) is defective |
| F0 238 | Gas valve or control box error – gas valve coils need checking |
| F0 239 | Control box or the heat control module (HCM) is defective – the control box connections need to be checked |
| F0 242 | Control box or the heat control module (HCM) is defective – the HCM and control box connections need to be checked |
| B7 257 | Control box or the heat control module HCM) is defective- the HCM and control box connections need to be checked |
| F0 258 | Control box or the heat control module (HCM) is defective – HCM or control box connections need to be checked |
| EH 258 | Control box or the heat control module (HCM) is defective – HCM or control box connections need to be checked |
| F1 259 | Control box or the heat control module (HCM) is defective – HCM or control box connections need to be checked |
| F0 262 | Control box or the heat control module (HCM) is defective – HCM or control box connections need to be checked |
| F1 263 | Control box or the heat control module (HCM) is defective – HCM or control box connections needs to be checked |
| 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 needs replacing |
| 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 needs replacing |
| F0 290 | The control box is defective – HCM needs checking as it might not be inserted properly or needs replacing |
| 328 | Internal error with the mains voltage – frequency may be inconsistent |
| 235 | Incompatible heat control module (HCM) software versions – control box needs the latest software |
| 356 | Low mains voltage – the voltage may be interrupted or inconsistent and needs checking |
| 360 | Heat control module (HCM) invalid – the inserted HCM does not correspond with the control box |
| A8 362 | Low mains voltage – the voltage may be interrupted, inconsistent, or heat control module (HCM) invalid |
| CC 800 | Outdoor sensor defect available when the accessory outdoor sensor is connected |
| A1 281 | Pump stock or running dry |
| E9 224 | Flue or high limit thermostat activated |
| D4 341 | Primary flow temperature rising too fast |
Greenstar Heatslave 11 error codes
| Fault Code | Description |
| E9210 | Maximum temperature thermostat or air pressure switch activated. Reset overheat thermostat or air pressure switch before resetting the boiler |
| E5218 | Flow temperature too high |
| E9219, 220 or 221 | Safety temperature too high, safety sensor short circuit or safety sensor open circuit |
| E2222, 223 or 233 | Flow sensor short circuit, flow sensor open circuit, or heat control module code plug missing or defective |
| F0237 or 238 | Software relay error – Resistors between plus X4 pins 3 & 5 disconnected or water in the burner control box |
| F0239 or 259 | Watchdog relay error or A/D reference relay error – If the error persists, change the control board |
| F0263 | Appliance powered off with locking fault present – press reset button to clear |
| D4271 | The temperature difference between flow and safety sensors exceeds the limit |
| E9276 or 277 | Flow temperature or safety temperature exceeds 95°C |
| F0278, 279 or 290 | Sensor test error, A/D convertor error, or A/D convertor reference error |
| E5332 | Primary flow has exceeded 105°C – primary sensor overheated |
| 9A360 | Incorrect HCM for boiler variant – replace with correct HCM |
| A7808 | DHW sensor defective – check and replace defect sensor as necessary |
| A0809 | Thermal store sensor defective – check and replace defect sensor as necessary |
| 9F855 or 856 | Burner lockout or 5 burner lockouts repeated resets. Check the burner and fuel supply, and ensure the oil supply is free of contaminants. After five 855 burner lockouts, code 856 is displayed. |
| H29 | Warning triangle and house symbol displayed on the controller – weather compensation activated but no weather sensor detected. |
| H27 | Warning triangle symbol displayed on the controller – DCW in sensor defect |
Greenstar Ri error codes
Including the Greenstar Ri 9/24 and the 27/30.
| Fault Code | Description |
| No light | No power at the control board |
| Light on | Appliance on but not operating during demand |
| Slow flash (mostly off flashes on) | Ignition lockout |
| Slow flash (mostly on flashes off) | Flue overheat or heat exchanger overheat |
| Fast flash | Volatile lockout sensor fan or code plug |
| 2 pulses | Check service mode switch is in minimum position |
| 5 pulses | Check service mode switch is in max position |
GB162 error codes
| Fault code | Description |
| 208 | The boiler is currently in chimney sweep mode. |
| 200 | The boiler is in heating mode. |
| 201 | The boiler is in domestic hot water (DHW) mode. |
| 202 | The boiler is waiting – there was a heat demand from the on-off or modulating control. |
| 203 | The boiler is on standby. |
| 204 | The boiler is waiting – the actual temperature is higher than the calculated or selected boiler temperature. |
| 212 | The temperature recorded by the flow temperature sensor or the safety sensor is rising too quickly. |
| 260 | The flow temperature sensor is not detecting a rise in temperature following a burner start. |
| 265 | The boiler is waiting in response to a heat demand – the boiler regularly switches to partial load. |
| 268 | The boiler is in a component test phase. |
| 270 | The boiler is modulating upwards. |
| 283 | The boiler is preparing for a burner start – the fan and pump are activated. |
| 284 | The gas valve has switched. |
| 305 | The boiler is waiting for domestic hot water (DHW) operation to end |
9A 361 | The burner control unit that has been fitted is not compatible with the KIM (boiler identification module). |
| A3 317 | There is a short circuit in the flue gas temperature sensor contacts. |
| C6 216 | The fan speed is too low. |
| CE 207 | The water pressure is too low. |
| CE 266 | The pump test failed. |
| D1 241 | The contacts of the boiler return temperature sensor have been interrupted. |
| D3 232 | The external switching contact has opened. |
| D4 213 | The actual temperature recorded by the flow temperature sensor or return temperature sensor is rising too quickly. |
| D4 286 | The boiler return temperature sensor has detected a return temperature higher than 105°c. |
| E2 223 | The flow temperature sensor contacts have been interrupted. |
| E9 210 | The temperature measured by the flue gas sensor is too high and is open. |
| E9 220 | The contacts for the safety temperature sensor have shorted or the safety temperature sensor has detected a temperature higher than 130°c. |
| E9 277 | The safety temperature sensor has measured temperature in excess of 95°c. |
| E9 285 | The boiler return temperature sensor has measured a temperature higher than 95°c. |
| E9 318 | The flue gas temperature sensor contacts have been interrupted. |
| EA 234 | The contacts of the gas valve have been interrupted. |
| EA 269 | The ignition device has been activated for too long. |
| GB162 | The ignition device has been activated for too long. |
| F0 278 | The sensor test has failed – cabling and plug sensors need checking. |
| F0 279 | The burner control unit, or KIM, is faulty – the control unit may need replacing. |
| F0 287 | The burner control unit, or KIM, has an error. |
| F7 328 | A brief power failure has occurred. |
| EC 256 | The burner control unit has an error. |
| H07 | The current water pressure is too low, limiting the performance in heat mode as well as domestic hot water (DHW) mode. |
| rE | The boiler resets. |