Worcester boiler fault codes
Boiler Fault Codes
Fault Codes
Worcester Boiler Fault Codes
Any boiler, whether a Worcester, Vaillant, Baxi, Potterton, Viessmann, Ideal or other brand, will often show you a fault code, usually made up of letters and numbers, such as E28 for example.
These fault codes are there to help our engineers locate the problem in a timely and efficient manner. Very often a single code may have several implications which our team can decipher, and repairs can be put underway.
The temptation is often to Google the code and try to solve the issue without ever calling an engineer. This can be both dangerous and costly. Our dedicated team of highly trained professional engineers has years of experience. Please note, it is actually illegal to work on a gas appliance without the relevant qualifications.
Below is a list of possible Worcester boiler fault codes that ALL require an engineer to visit.
Boiler error codes
Greenstar 27/30 I System Boilers
CDi Classic Regular
Greenstar I System or Combi
GB162 Commercial Boiler
Worcester boiler fault codes If you are unsure please don’t hesitate to speak to one of our team.
CDI Classic Combi
Fault Description | System Behaviour |
| A1 | Water is leaking or the pump needs replacing or freeing due to the pump running dry |
| A7 | The hot water negative thermistor coefficient (NTC) sensor is defective – the hot water sensor or connecting leads need checking |
| A8 | Break communication to FX sensor controls electrical connections need checking |
| A7 | The hot water negative thermistor coefficient (NTC) sensor is defective – the hot water sensor or connecting leads need checking |
| B1 | Code plug not detected |
| C6 | Fan speed too low – the fan lead and connector need checking and may need replacing |
| E2 | Central heating (CH) water flow negative thermistor coefficient (NTC) sensor defective check CH flow NTC sensor and connection leads |
| A7 | The hot water negative thermistor coefficient (NTC) sensor is defective – the hot water sensor or connecting leads need checking |
| E9 | Safety temperature limiter in central heating (CH) flow has tripped the system pressure or safety temperature limiter needs checking |
| EA | Flame not detected due to a gas issue – the gas supply, power supply or igniter, electrode and lead need checking – contact a Gas Safe installer |
| F0 | Internal error – electrical connector contacts or programmer interface module – check ignition leads are not loose |
| F7 | Flame detected even though the appliance is switched off – check the electrode assembly is dry and the pcb and flue are clear |
| FA | Flame detected after gas shut off – the gas valve needs checking – hire a Gas Safe installer |
| FD | Reset button pressed by mistake – press reset button again |
CDI Highflow Combi
Fault Description | System Behaviour |
| A1 | Pump dry run detection or pump is running in air the system pressure needs checking |
| 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 |
| 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 appliance has been shut off |
| FA | Flame detected after gas shut off |
| FD | Reset button pressed – try pressing the reset button again |
Worcester Bosch CDi Compact / Greenstar 25/30 Si Combi / Greenstar 27/30 I system Boiler Error Codes
Worcester Bosch boiler fault codes and error codes
Fault Description | System Behaviour |
| 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 |
| F0 237 | Internal error |
| F7 228 | Flame error – false flame or flame detected before burner starter |
| FA 306 | False flame fault – flame detected after burner stop |
| FD 231 | Mains power fault – electrical power interruption |
| FA 364 | Gas valve EV2 leak test failed – gas valve leak |
| FA 365 | Gas valve EV1 leak test failed |
| A1 281 | Pump stuck or running with air in the system |
| C1 264 | Airflow stopped during operation |
| C4 273 | Airflow present during last 24 hours |
| D1 240 | Return sensor short circuit |
| D4 271 | Temperature difference between flow and safety sensor exceeds limit |
| E9 224 | Max thermostat activated – flue gas thermostat overheat |
| EA 277 | No ionisation detected after ignition |
| 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 |