Worcester boiler repair in London
We repair current and older Worcester Bosch boilers. Ring us, day or night.
- Worcester Greenstar repaired and serviced
- All our engineers are Gas Safe registered
Makes we repair
How does booking a Worcester Bosch repair work, and what does it cost?
Booking: ring us any time, day or night, or send your details and we ring you back. We'll ask what the boiler is doing, and its model and any code on the display if you can see them. You don't need to know what's wrong. Finding the fault is the engineer's job. Then we tell you when an engineer can come, anywhere in Greater London.
What it costs: a repair's price depends on the part it needs, how long the job takes and when it's done. Our rates are higher in the evening, overnight and at weekends. Once the engineer has found the fault, the rate for the repair is agreed in writing before any work starts.
What happens on a Worcester Bosch repair visit?
A repair visit has three stages.
1. Before anything is touched
The engineer covers the floor around the boiler and asks what you have seen and heard since you rang.
2. Finding the fault
The engineer tells you which part has failed, whether they have it with them or must order it, and how long the work should take. No work is done until you say yes.
3. The repair
The engineer fits the part and checks the boiler runs as it should before leaving. The repair is guaranteed for 12 months, covering the parts we fit, the labour and any return visit.
What goes wrong on Worcester Bosch boilers most often?
Worcester Bosch's own help pages come back to the same few problems:
- A blocked or frozen condensate pipe. The boiler gurgles as it starts, locks out again and again, and shows EA or a flashing light. In a hard frost it is the commonest reason a condensing boiler stops.
- Losing pressure. Topping up once or twice a year is normal. More often means water is escaping, from a joint, a radiator valve or the pressure relief valve, and the system needs an engineer.
- Pressure rising, and radiators that need bleeding again and again. Worcester treats this as urgent. Gas is forming from corrosion inside the system, which needs cleaning.
- Codes that aren't faults. A service reminder, or the slow start while the condensate trap refills.
Whichever it is, we'll ask what the boiler is doing when you ring.
Sources: Worcester Bosch's help pages on condensate pipes, gurgling, losing pressure, topping up and the display's symbols, and the user guides for the Greenstar 4000 and 8000+.
What is the display or the light telling you?
The codes Worcester's own guides come back to most. Open one to see what it means and what you can do.
EA 227Worcester EA 227 (Greenstar i System, Si and CDi Compact) or 227 (8000+, 8000 Life, 4000, 2000, 1000): no flame
What it means: the boiler tried to light and found no flame. On the Greenstar i System, Si and CDi Compact, the code is EA with 227. Those boilers try four times, 30 seconds apart, before they lock out. On the 8000+, 8000 Life, 4000, 2000 and 1000, the code is 227 alone. On a CDi Classic, a Highflow, a floor-standing FS CDi or a 2012 Greenstar 24 or 28, EA alone means no flame was detected. EA with 229 is a different fault, set out next.
Possible causes, as the 8000+ manual lists them:
- the gas supply to the home and the boiler
- the gas valve
- something blocking the fan's air intake
- a blocked condensate trap or a frozen condensate pipe
- a blocked flue
- a blocked heat exchanger
- the burner
- the ignition and flame-sensing parts and their leads
What you can do: the user guides give these steps.
- See whether your other gas appliances work, and whether a prepayment meter has credit.
- Where it is safe, look at the condensate pipe's outlet and the flue outlet for ice or a blockage.
- Thaw a frozen condensate pipe at ground level with warm, never boiling, water.
- Reset once, as the user guide for your range shows.
EA 229Worcester EA 229 (Greenstar i System, Si and CDi Compact) or 229 (8000+, 8000 Life, 2000, 1000): the flame went out while the boiler was running
What it means: the flame lit, then went out while the boiler was running. On the Greenstar i System, Si and CDi Compact, EA with 229 is a locking fault, so the boiler stays off until it is reset. On the 8000+, 8000 Life, 2000 and 1000, 229 alone is a blocking fault, and the boiler tries again by itself.
Possible causes, as the manuals list them:
- On a Compact: water in the burner's sump from a blocked condensate trap, or a strong wind blowing into the flue.
- On the 8000+: the gas supply and its pressure at the boiler, the mix of gas and air, or the flame-sensing electrode and its lead. On LPG, an empty or newly filled tank.
What you can do:
- See whether your other gas appliances work.
- Where it is safe, see whether the condensate pipe's outlet is frozen or blocked.
- Thaw a frozen pipe at ground level with warm, never boiling, water.
- On a Compact, reset once with the reset button.
E9 224Worcester E9 224 (Greenstar i System, Si and CDi Compact) or 224 (8000+, 8000 Life, 4000, 2000, 1000): an overheat safety device has tripped
What it means: a safety device that guards against overheating has tripped. Which one depends on the range:
- Greenstar i System, Si and CDi Compact: E9 with 224 is the flue gas thermostat. Those manuals give E9 with 219, 220 or 221 for the heat exchanger's own safety sensor. E9 with 276, 277 or 285 is water above 95°C. Each is in the list below.
- 8000+, 8000 Life and 4000: 224 alone is the flue gas or heat exchanger high-limit thermostat.
- 2000 and 1000: 224 is the safety temperature limiter.
- CDi Classic, Highflow and floor-standing FS CDi: E9 alone is the safety limiter on the heating flow.
- 2012 Greenstar 24 or 28: E9 is the heat exchanger or flue gas limiter.
Possible causes, as the manuals list them: on a Compact, the flue gas thermostat overheating. On the 8000+, the manual lists:
- a loose lead or a faulty limiter or wiring
- the water running hotter than the boiler reads
- low system pressure
- air in the system or the boiler
- a seized pump
- a blockage restricting the flow through the boiler or the pipes
What you can do: on an 8000+, 8000 Life, 4000, 2000 or 1000, low pressure is one of the causes the manual lists.
- Look at the gauge with the system cold.
- If it reads low, top it up as the user guide shows.
- Reset once.
On a Compact, 224 is the flue gas thermostat. Reset once with the reset button, and leave the rest to an engineer.
1017Worcester 1017 (Greenstar 8000+, 8000 Life, 4000): the system pressure is low
What it means: the water pressure in the heating system is low. 1017 shows on the Greenstar 8000+, 8000 Life and 4000, whose manuals file it with the maintenance codes. The 4000's user guide shows it once the gauge reads below 0.8 bar. If the pressure falls further, the same boilers show 2971 and stop.
Possible causes, as the manual lists them: too little water in the system, then the pressure sensor or its wiring.
What you can do: with the system cold, top up at the filling link to between 1 and 1.5 bar, as the user guide shows. If the pressure keeps dropping, ring us. Water is escaping somewhere, and the fresh water dilutes the inhibitor that protects the system.
2971Worcester 2971 (Greenstar 8000+, 8000 Life, 4000, 2000): the pressure is too low and the boiler has stopped
What it means: the system pressure has fallen too low for the boiler to run. The boiler stops, and starts again by itself once the pressure is back (a blocking fault). 2971 shows on the Greenstar 8000+, 8000 Life, 4000 and 2000. On the 4000, it comes on when the pressure falls to between 0.6 and 0.3 bar.
Possible causes, as the manuals list them:
- too little water in the system
- on a boiler with Worcester's Intelligent Filling System, an accessory, a problem with the automatic filling
- the pressure sensor or its wiring
What you can do: with the system cold, top up at the filling link to between 1 and 1.5 bar, as the user guide shows. An Intelligent Filling System tops up by itself, and its settings are the installer's. If 2971 comes back, ring us. Water is escaping somewhere.
A1 281Worcester A1 281 (Greenstar i System, Si and CDi Compact) or 281 (8000+, 8000 Life, 4000, 2000): the pump
What it means: the heating pump is stuck or running with air in it. The code depends on the range:
- Greenstar i System, Si and CDi Compact: A1 with 281.
- 8000+, 8000 Life and 4000: 281 alone.
- 2000: 281, which its manual gives as the pump's pressure rise being too low.
On each of these ranges, the code is a blocking fault. The boiler stops, and starts again by itself once the cause has gone. A Compact shows nothing on the display for a blocking fault. Its number is in the info menu, under the spanner button. On a CDi Classic, A1 alone means the pump has run dry.
Possible causes, as the manuals list them:
- On a Compact: little or no water in the system.
- On the 8000+: low pressure in the system, air locks, a blockage or restriction, the pump's signal cable, or the pump itself.
What you can do: look at the pressure gauge with the system cold. If it is low, top up to between 1 and 1.5 bar, as the user guide shows.
D5Worcester D5 (Highflow, FS CDi Regular, 2012 Greenstar 24/28): a different fault on each range
What it means: D5 has no single meaning on Worcester boilers, so we'll ask for the model. On a Greenstar Highflow 440CDi or 550CDi, or a floor-standing Greenstar FS 30CDi or 42CDi Regular, d5 is a fault with the condensate pump. On a 2012 Greenstar 24 or 28 combi, d5 is a faulty temperature sensor on a low-loss header outside the boiler. Worcester's installer guidance lists D5 among the codes some of its boilers may show when the condensate pipe freezes, without naming the models.
Possible causes, as the manuals list them:
- On a Highflow or FS CDi: the condensate pump.
- On the 24 or 28: the sensor or its cable.
In a frost, a frozen condensate pipe is one possible cause, not what the code means.
What you can do: in a frost, follow these steps.
- Look along the condensate pipe where it runs outside.
- Thaw a frozen pipe at ground level with warm, never boiling, water.
- Reset the boiler as the user guide shows.
The Highflow's and FS CDi's user guides list d5 among the faults to leave to an engineer. For the pump or a sensor, or if D5 comes back, ring us.
C6Worcester C6 (Greenstar i System, Si and CDi Compact, CDi Classic, Highflow, FS CDi, 2012 24/28): the fan
What it means: C6 is a fan fault, and its detail depends on the range:
- Greenstar i System, Si and CDi Compact: C6 comes with a number. 215 means the fan is running too fast, and 216 too slow. Those manuals give the fan not running as C7 with 214, and no airflow as C7 with 217.
- CDi Classic, Highflow and floor-standing FS CDi: C6 alone means the fan speed is too low.
- 2012 Greenstar 24 or 28: C6 means the fan is not running.
Possible causes, as the 24 and 28 manual lists them: the fan's lead and plug, then the fan itself.
What you can do: reset once, as the user guide for your range shows. If C6 comes back, ring us. The fan and its wiring are inside the case.
2980Worcester 2980 (Greenstar 8000+, 4000, 1000): a super lock-out
What it means: 2980 is a super lock-out. The boiler has locked itself out after repeated resets of a fault that may be safety-critical, and stays off until an engineer clears it. The Greenstar 8000+ and 4000 manuals give five locking faults reset in the space of 15 minutes. The 1000's manual gives six resets in the space of 15 minutes. 2981 follows when the power is turned off and on, and means the boiler is still locked. The 8000+, 4000, 2000 and 1000 manuals list 2981.
What you can do: nothing at home. The 8000+'s user guide says to call a qualified heating engineer straight away, and not to try to clear it yourself. The heating and hot water stay off until an engineer has put it right.
A21Worcester A21: a code from the Greenstar heating controls, often a lost signal
What it means: a code from the Greenstar heating controls, often a lost signal. A21 shows on the Comfort I RF, the Comfort II RF and the Sense I, not in the boiler's own list of faults. A number may show with it:
- Comfort I RF: A21 with 1001 means no radio signal. 1007 comes with A27, when the control can't communicate with the boiler.
- Sense I: A21 with 1001 means the thermostat is set up wrongly for heating circuit 1.
- Comfort+ II RF: a lost signal shows as 1007.
Every cause of A21, and what fixes it, is on the A21 fault code page.
MoreEvery other Worcester Bosch code, range by range
Worcester's codes differ from range to range. Each list below belongs to the ranges in its title, from their own installation manuals. The codes with a panel above aren't repeated here. We'll ask for the model when you ring.
Greenstar 8000+ and 8000+ Style (installation and maintenance instructions 6721108973, 2025, pages 74 to 79)
The display shows a number with a line of text. A locking fault keeps the boiler off until it is reset. A blocking fault stops it for a while, and it starts again by itself once the cause has gone. The Greenstar 8000 Life's manual (6720883865, 2021) prints the same numbers and words, less 2927, 2980 and 2981.
214Locking: the fan stopped during the safety time
What the manual lists
A reset and a fresh call for heat, then the fan's voltage and wiring, its speed control, and the control board
228Locking: a flame signal with no flame there
What the manual lists
The flame sensor and its lead, the earth connections, the siphon and any water in the sump, the gas valve, then the control unit
232Blocking: the boiler is held off by an external switch contact
What the manual lists
The external switch connection, which the manual says isn't used in the UK. A condensate lifting pump's safety contact, or an external temperature monitor, its setting or its cable
233Locking: the boiler's identification module (the code plug) or its electronics
What the manual lists
A wrong or damaged code plug
234Locking: an electrical fault on the gas valve
What the manual lists
The gas supply at the valve, loose connections, the wiring, the valve's voltage and resistance, and water on its connections. Then the gas valve or the board
235Locking: the electronics and the boiler's identification don't match
What the manual lists
The code plug or the burner control
237Locking: a system fault
What the manual lists
The code plug, then the control board
238Locking: a fault in the boiler's electronics
What the manual lists
The gas supply at the valve, the gas valve's connections, wiring, voltage and resistance, then the board
242A fault in the boiler's electronics
What the manual lists
Whether it happens again after a restart, and if it does, the burner control board
244, 245, 249, 250, 251, 252, 253, 254, 258A fault in the boiler's electronics or basic controller
What the manual lists
A restart, the board's connections, the code plug, then the control board
257, 259Locking: a fault in the boiler's electronics or basic controller
What the manual lists
A restart, the board's connections, the code plug, then the control board
262, 263Locking: a fault in the boiler's electronics or basic controller
What the manual lists
A restart, the board's connections, the code plug, then the control board
269Locking: a fault in the flame monitoring
What the manual lists
A restart, the board's connections, then the control board
306Locking: a flame signal after the gas was shut off
What the manual lists
Whether the gas pressure drops back as the valve closes, a gas valve letting gas by, then the board
360Locking: a fault in the boiler's electronics or basic controller
What the manual lists
A wrong or damaged code plug
362Locking: the boiler's identification module or its electronics
What the manual lists
A wrong or damaged code plug
363Locking: a fault in the boiler's electronics or basic controller
What the manual lists
The flame-sensing lead, the electrodes, then the control unit
604A fault in the burner control unit
What the manual lists
Whether it happens again after a restart, and if it does, the burner control board
815Maintenance code: the low-loss header's temperature sensor is faulty
What the manual lists
Whether the setting was switched on by mistake, moisture on the connectors, or a board fault
1010Filed by the manual as an operating code: no communication over the EMS bus, the link to the display and the controls
What the manual lists
The display unit and its plug, a Key's connections, the bridging links, mains wiring run beside the bus wires, then the board
1019The wrong type of pump detected
What the manual lists
The pump's communication wire, or a pump that isn't the right modulating type
1021Blocking: the hot water or cylinder temperature sensor is faulty
What the manual lists
The sensor, its plug, its resistance and its wiring
1025The return temperature sensor is faulty
What the manual lists
The manual notes this sensor isn't fitted on this boiler
1037Maintenance code: the outside temperature sensor is faulty, and the heating runs in a back-up mode
What the manual lists
Whether weather compensation is meant to be on, the sensor's position, its connections, its resistance and its cable
1065Blocking: the system pressure sensor is faulty or unplugged
What the manual lists
The sensor's plug, its wiring and voltages, then the sensor
1068Maintenance code: the outside temperature sensor or lambda probe is faulty
What the manual lists
The sensor's plug, its resistance and wiring, then the sensor
1075Maintenance code: the heat exchanger temperature sensor has a short circuit
What the manual lists
The sensor's plug, its resistance and wiring, then the sensor or the board
1076Maintenance code: the heat exchanger temperature sensor is disconnected
What the manual lists
The sensor's plug, its resistance and wiring, then the sensor or the board
2085Locking: an internal fault
What the manual lists
A reset, 30 seconds with the power off, the mains voltage and polarity, then the board
2908Locking: a fault in the boiler's electronics or basic controller
What the manual lists
Whether it happens again after a restart, and if it does, a new burner control board
2910Locking: a fault in the flue system
What the manual lists
The flue for a blockage, the flue integrity test, water in the sump and the siphon
2914, 2915, 2916A fault in the boiler's electronics
What the manual lists
Whether it happens again after a restart, and if it does, the burner control board
2920Locking: a fault in the flame monitoring
What the manual lists
A possible board fault. The manual gives no checks
2923, 2924, 2925, 2926, 2927Locking: a fault in the boiler's electronics
What the manual lists
The gas valve's voltage, its coils and the wiring, then the gas valve or the board. The 8000 Life's manual lists 2923 to 2926
2928An internal fault
What the manual lists
Whether it happens again after a restart, and if it does, the burner control board
2931A fault in the boiler's electronics or basic controller
What the manual lists
Whether it happens again after a restart, and if it does, the burner control board
2940Locking: a fault in the burner control unit
What the manual lists
Whether it happens again after a restart, and if it does, the burner control board
2946Locking: the wrong code plug detected
What the manual lists
The code plug, its part number and its connections
2948Blocking: no flame signal at low output
What the manual lists
The burner relights by itself after a purge, and strong wind can cause it. If it keeps happening, the combustion settings, the flue and its terminal
2949Blocking: no flame signal at high output
What the manual lists
Strong wind, or flue gas drawn back in. The flue and where its terminal sits, the combustion settings, the burner and flue seals, and the gas pressure at full output
2950Blocking: no flame signal after the start-up sequence
What the manual lists
The combustion settings, the burner and heat exchanger seals, and the gas pressure at full output. The burner relights by itself after a purge
2951Locking: the flame has been lost too many times
What the manual lists
The blocking faults that led to it, in the fault history. Air left in the gas pipe. Undersized gas pipes, falling gas pressure, condensate pipes or flues run wrongly, or wiring. Running with the combustion case off can cause it
2952Locking: an internal fault while testing the flame signal
What the manual lists
Whether it happens again after a restart, and if it does, the burner control board
2955Blocking: the boiler doesn't support the hydraulic settings made
What the manual lists
The installer's hydraulic settings. It clears when the power is turned off
2957Locking: a fault in the boiler's electronics
What the manual lists
Whether it happens again after a restart, and if it does, a new burner control board
2961, 2962Locking: no signal from the fan
What the manual lists
The fan's mains voltage, its wiring and its speed signal, then the fan or the board
2963Blocking: the heat exchanger sensor, or that sensor and the flow sensor, faulty
What the manual lists
Water flowing and the system full, air locks, then the sensor, its plug, its resistance and its wiring
2965Blocking: the flow temperature is too high
What the manual lists
Water flowing and the system full, air locks, and the isolating valves
2966Blocking: the water in the heat exchanger is heating up too fast
What the manual lists
Water flowing and the system full, air locks, the isolating valves, and whether the pump runs freely with power
2969The most refills allowed has been reached
What the manual lists
The limit on refills has been reached
2970Blocking: the pressure in the heating system has dropped too fast
What the manual lists
Too many sudden pressure drops in a short time, which venting the system with the Intelligent Filling System switched on can cause. The engineer refills by hand and sets the pressure
2972The mains voltage is too low
What the manual lists
The supply voltage at the boiler
2981Locking: the boiler is still in a super lock-out (2980) after its power was turned off and on
What the manual lists
The engineer's steps once the fault behind 2980 has been found and put right
Greenstar 8000+, 8000+ Style and 8000 Life: status and service messages, not faults
200Status: heating
What the manual lists
An operating message, not a fault
201Status: hot water
What the manual lists
An operating message, not a fault
202Status: anti-cycle mode, a pause so the boiler doesn't fire too often
What the manual lists
An operating message, not a fault
203Status: standby, with nothing calling for heat
What the manual lists
An operating message, not a fault
204Status: the water in the boiler is hotter than the temperature set, so the burner is off
What the manual lists
The manual's operating code
208Status: chimney sweep (test) mode requested
What the manual lists
An operating message, not a fault
265Status: less heat is being asked for than the boiler is giving
What the manual lists
An operating message, not a fault, though the manual files it as blocking
268Status: a relay test is running
What the manual lists
A status message
273Status: the burner and fan have been stopped for a time
What the manual lists
A status message, though the manual files it as blocking
283Status: the burner is starting
What the manual lists
An operating message, not a fault
284Status: the gas valve is opening
What the manual lists
An operating message, not a fault
305Status: hot water anti-cycle mode, keeping the hot water warm
What the manual lists
The diverter valve held on hot water for a time. The engineer looks for false calls for hot water
357Status: the venting programme is running
What the manual lists
An operating message, not a fault
358Status: the pump and the three-way valve are being moved so they don't seize
What the manual lists
An operating message, not a fault
2956Status: the hydraulic set-up at the boiler is active
What the manual lists
The installer's settings. It clears when the power is turned off
2968Status: the automatic filling is topping up the pressure
What the manual lists
The filling valve letting fresh water into the heating
1013Service reminder: the maximum combustion point set for servicing has been reached
What the manual lists
The maintenance menu, reset after the service
1018Service reminder: the service interval has run out
What the manual lists
The service date set in the menu, reset after the service
1023Service reminder: the maximum running time, standby included, has been reached
What the manual lists
The maintenance menu, reset after the service
1070Service reminder: a service is due on the date shown
What the manual lists
An early reminder. The maintenance menu, reset after the service
1071Service reminder: a service is due now
What the manual lists
The maintenance menu, reset after the service
1072Service reminder: a service is overdue
What the manual lists
The maintenance menu, reset after the service
Greenstar i System Compact, Si Compact ErP and CDi Compact ErP (installation and servicing instructions 6720807726, 2013, pages 67 and 68; 6720813278, 2015, pages 70 and 71; 6720813276, 2015, pages 72 and 73)
Each fault is two characters with a three-figure cause number, such as C7 and 214. People type it either way, C7 214 or 214. A locking fault flashes with a warning triangle until the reset button is pressed. A blocking fault stops the boiler with nothing on the display, and clears by itself. Its number is in the info menu, under the spanner button. The i System and Si Compact manuals add two maintenance codes, which need attention but don't stop the boiler:
- H11: the hot water outlet sensor is faulty, so the hot water runs with less control.
- H13: the service interval set on the boiler has run out.
9A 362Locking: the heat control module (HCM). Not in the CDi Compact's table
What the manual lists
The wrong module fitted
9U 233Locking: the heat control module
What the manual lists
The code plug, faulty or not connected
b7 257Locking: an internal error
What the manual lists
A new control board
C7 214Locking: the fan isn't running
What the manual lists
The fan
C7 217Locking: no airflow after a set time
What the manual lists
The fan not running, or the airflow blocked
D1 240Locking: the return sensor
What the manual lists
A wet or damaged sensor. The boiler blocks for 300 seconds first
D1 241Locking: the return sensor
What the manual lists
A disconnected or damaged sensor. The boiler blocks for 300 seconds first
D1 286Locking: the return water is too hot
What the manual lists
The boiler overheating
E2 222Locking: the flow sensor has a short circuit
What the manual lists
A shorted or damaged sensor
E2 223Locking: the flow sensor is open circuit
What the manual lists
A disconnected or damaged sensor
E5 218Locking: the flow temperature is too high
What the manual lists
The flow sensor has overheated
E5 332Locking: the flow sensor has gone above 110°C
What the manual lists
The flow sensor has overheated
E9 219Locking: the heat exchanger's safety sensor is too hot
What the manual lists
The main heat exchanger has overheated. The manual gives 105°C
E9 220Locking: the safety sensor has a short circuit
What the manual lists
The heat exchanger's high-limit sensor has failed
E9 221Locking: the safety sensor is open circuit
What the manual lists
The boiler doesn't recognise that sensor
EA 234Locking: a gas valve error
What the manual lists
The gas valve's coil disconnected
EA 261Locking: an ignition timing error
What the manual lists
No flame in the first 4 seconds of lighting
F0 237 to 239, 242 to 256, 258, 259, 262, 263, 267, 272, 279, 290An internal error
What the manual lists
An engineer's call to Worcester's technical helpline
278Locking: a sensor test failed
What the manual lists
The safety sensors are checked at power-up, and the check failed
280Locking: a recycle time error
What the manual lists
A timing fault in the purge after the burner stops
338Locking: too many short burner starts without confirmation
What the manual lists
The pump not detecting water
F7 228Locking: a false flame, seen before the burner started
What the manual lists
A flame signal before the burner lit
F7 328Locking: an internal error
What the manual lists
A new control board
FA 306Locking: a false flame after the burner stopped
What the manual lists
A flame signal after the burner stopped
FD 231Locking: a mains power error
What the manual lists
The electricity supply was interrupted
FA 364Locking: the gas valve's second (EV2) leak test failed
What the manual lists
A gas valve leak
Fb 365Locking: the gas valve's first (EV1) leak test failed
What the manual lists
A gas valve leak
C1 264Blocking: the airflow stopped while the boiler was running
What the manual lists
The fan has stopped
C4 273Blocking: airflow for the whole of the last 24 hours
What the manual lists
The fan running without a break for 24 hours
D1 240Blocking: the return sensor has a short circuit
What the manual lists
A wet sensor. After 300 seconds, the locking D1 240
D1 241Blocking: the return sensor is disconnected
What the manual lists
After 300 seconds, the locking D1 241
D4 271Blocking: the flow and safety sensors read too far apart
What the manual lists
The two should be within 15°C of each other
E9 276Blocking: the flow temperature is above 95°C
What the manual lists
The boiler waits for it to cool. If it doesn't, a locking fault
E9 277Blocking: the safety sensor is above 95°C
What the manual lists
The heat exchanger overheating. If it doesn't cool, the locking E9 219
E9 285Blocking: the return temperature is above 95°C
What the manual lists
The burner stops. If the temperature still rises after 2 seconds, the locking D1 286
EF 349Blocking: boiling detected in the heating, with a large gap between flow and return at the lowest burner rate
What the manual lists
More than 18°C between flow and return at minimum output
212Blocking, with no code on the display: the safety or flow temperature is rising too fast
What the manual lists
An air lock or too little water
213Blocking, with no code on the display: too great a difference between flow and return
What the manual lists
An air lock or too little water
260Blocking, with no code on the display: no rise in temperature after the burner starts
What the manual lists
A disconnected sensor, or no water
380Blocking, with no code on the display: the incoming cold water is warmer than the hot water outlet
What the manual lists
The output held off until the inlet is cooler than the outlet
Greenstar 24 and 28 combi, GC 47-406-32 and 47-406-33 (installation, commissioning and servicing instructions 6720800945, 2012, page 43)
Two characters flash on the display.
A7The hot water temperature sensor is faulty
What the manual lists
The sensor and its lead, for a break or a short circuit
A8A communication fault
What the manual lists
The lead to the controls on the bus
AdThe cylinder temperature sensor isn't detected
What the manual lists
The sensor and its lead
b1The code plug isn't detected
What the manual lists
The code plug, seated properly, tested or replaced
b2, b3Internal data error
What the manual lists
The manual sends the engineer to its servicing instructions
CCThe outside temperature sensor isn't detected
What the manual lists
The sensor and its lead, for a break
d3An external limiter has tripped
What the manual lists
An external temperature limiter, or a missing wire link on its terminals
E2The heating flow temperature sensor is faulty
What the manual lists
The sensor and its lead
F0An internal fault
What the manual lists
The electrical connectors and ignition leads, the gas and air mix, then the board
F1Internal data error
What the manual lists
The manual sends the engineer to its servicing instructions
F7A flame is detected with the boiler switched off
What the manual lists
The electrodes, the flue, and damp on the board
FAA flame is detected after the gas was shut off
What the manual lists
The gas valve, the condensate trap, the electrodes and the flue
FdThe reset button was pressed by mistake
What the manual lists
Press reset again
Each list was checked against its manual, from Worcester Bosch's own literature downloads, on 11 October 2026.
Sources, checked on 11 October 2026: Worcester Bosch's user guides and installation manuals for each range, the CDi Classic's service booklet, its installer guidance on frozen condensate pipes, and the guides for its Comfort I RF, Comfort+ II RF and Sense I controls.
Which Worcester Bosch boiler do you have, and how does it show a fault?
Worcester Bosch is one of the makes we fit most, and every Greenstar shows a fault in one of five ways. The model name is on the front of the boiler, or on the data label inside its door. We'll ask for it when you ring.
Not every code is a fault. The display shows these too:
- a service reminder
- a boiler running at low power for about 15 minutes after the power comes back, to refill its condensate trap
- codes that show normal running
We'll ask what it shows.
How do you reset a Worcester Bosch boiler?
A Worcester Bosch boiler resets in a different way on each range:
- 8000+, 8000 Life and 4000: press the two arrow keys together until "Reset" shows.
- 2000 and 1000: switch the boiler off and on, or press both arrow keys until the H and the exclamation mark go.
- i, Si and CDi Compact: press the reset button.
- CDi Classic: hold the reset button for 3 seconds, or 5 after thawing a condensate pipe.
- Ri: turn the heating knob to RESET, hold it for about 5 seconds, then turn it back.
- i Junior: press and hold the flashing reset button for more than 2 seconds.
With the system cold, the pressure gauge should read 1 to 1.5 bar. Below 1 bar, the user guide shows how to top it up at the filling link.
If the code comes back after a reset, ring us rather than resetting again. On a Greenstar 8000+ or 4000, five resets of a locking fault in the space of 15 minutes lock the boiler. That is the super lock-out, 2980, for a fault that may be safety-critical. The boiler then stays off until an engineer clears it. The 1000's manual gives six resets.
A frozen condensate pipe can be thawed with warm, never boiling, water, where the pipe is at ground level and easy to reach. When a boiler won't fire up, and frozen condensate pipes.
Sources: Worcester Bosch's user guides for each range and the i Junior's installation manual, the installation manuals for the Greenstar 8000+, 4000 and 1000, and its leaflet on frozen condensate pipes.
Is your Worcester Bosch boiler still under guarantee?
Worcester Bosch's guarantee depends on the model and who fitted it:
- A Greenstar 8000+ has 8 years, or 10 with a Greenstar system filter. When a Worcester Accredited Installer fits it with the filter, it has up to 12.
- A 4000, a CDi Compact, an i System Compact or an Ri has 7, 8 or 10 years on the same terms.
- A 2000 has 7 years and a 1000 has 5, each with a system filter.
The boiler must be registered within 30 days of fitting, and serviced every year.
While the guarantee runs, Worcester's own engineers repair the boiler. Worcester doesn't pay other engineers' invoices, or for repairs it hasn't agreed in writing first. Its terms leave out:
- resetting
- topping up the pressure
- thawing a frozen condensate pipe
Worcester can also charge a call-out when its engineer finds no fault.
A boiler still under its maker's guarantee is usually repaired by the maker, at no charge, so ring Worcester Bosch first. Once the guarantee has ended, or for a fault it doesn't cover, ring us. We are an independent firm, with no connection with Worcester Bosch.
What does a Worcester Bosch boiler service cover?
Worcester Bosch asks for a service every year to keep the guarantee valid. Worcester's own engineers or any Gas Safe registered engineer can do it. The service is recorded in the Benchmark service record at the back of the manual.
A Worcester Bosch service covers:
- the flue
- the combustion readings
- the fan pressure test, which shows whether the heat exchanger needs cleaning
- the condensate trap
- the gas pressure
- a test of the inhibitor in the heating water
A service reminder on the display, such as 1070 to 1072, H13 or SE, means a service is due.
We service every Worcester Bosch model, and give you the rate on the call. What a boiler service includes, check by check.
Do you cover my part of London?
Yes: we travel all over Greater London, day and night, to repair Worcester Bosch boilers in every borough, north and south of the Thames. Pick your side of the river to see the areas.
North of the river
Every borough north of the Thames: Barnet and Enfield at the top, Hillingdon in the west, Havering in the east, and central London in between.
South of the river
Every borough south of the Thames: Richmond and Kingston in the west, Bexley in the east, and down through Croydon to Sutton and Bromley.
The other makes we repair
Every main make, combi, system and regular. Pick yours for its common faults, its codes and how we repair it.
Questions about Worcester Bosch boilers
Do I need to know what's wrong with my Worcester Bosch boiler before I ring?
No. Ring and say what the boiler is doing, or what you can see or hear, and we'll ask the rest. Finding the fault is the engineer's job.
Do you charge more in the evening or at weekends?
Yes. Our rates are higher in the evening, overnight and at weekends.
Can you repair an older Worcester Bosch boiler?
Usually, yes. It depends on the boiler's condition and whether its parts are still made. We'll ask for the model when you ring.
Is my Worcester Bosch boiler worth repairing?
Often, yes. Age alone doesn't decide it. What decides it is the rate for the repair against a new boiler, and how often the boiler has failed. The engineer gives you the rate for the repair, and the choice is yours. When a new boiler makes more sense.
Will a repair affect my Worcester Bosch guarantee?
While the guarantee runs, ring Worcester Bosch first. The maker usually repairs a boiler under guarantee itself, and its terms say who may work on it. Once it has ended, any Gas Safe registered engineer can repair it.
Do you fit Worcester Bosch's own parts?
Yes, the maker's own parts wherever they are available. Each repair is guaranteed for 12 months, covering the parts we fit, the labour and any return visit.
How much does a Worcester Bosch boiler repair cost?
The cost of a repair depends on the part, how long the job takes and when it's done. The rate is agreed in writing before the repair starts. How our rates work.
Why does my Worcester Bosch boiler keep losing pressure?
Usually water escaping from the system: a joint, a radiator valve, or the pressure relief valve, whose pipe drips outside. Topping up once or twice a year is normal. More often needs an engineer, because fresh water also dilutes the inhibitor that protects the system.
Why is my Worcester Bosch boiler gurgling?
Worcester links gurgling as the boiler starts to a blocked or frozen condensate pipe, often with EA on the display or repeated lock-outs. We'll ask what the display shows when you ring.
What does EA 227 mean on a Worcester boiler?
EA 227 means the boiler tried to light and found no flame. A Greenstar i System, Si or CDi Compact shows it as EA with 227. An 8000+, 8000 Life, 4000, 2000 or 1000 shows 227 alone. EA with 229 is a different fault, a flame lost while the boiler was running.
Can any Gas Safe engineer service my Worcester Bosch boiler under guarantee?
Yes. Worcester's terms let any Gas Safe registered engineer do the yearly service, as long as it is recorded in the Benchmark service record. Repairs under the guarantee are Worcester's own.
Who makes Worcester Bosch boilers?
Worcester, founded in 1962 and part of the Bosch Group since 1996, now in the Bosch Home Comfort Group. Its gas boilers are made at its headquarters in Worcester.
Don't know what has failed? You don't have to.Ring and say what you can see or hear. Finding the fault is our job.
Calls answered 24 hours a day
A real person answers and gives you the rate on the call. No work starts until you say yes, and repairs are guaranteed for 12 months: parts, labour and any return visit.
