Worcester Boiler Fault Codes Explained
Not every number on a Worcester Bosch display is a fault. Worcester's code table mixes normal status messages with faults that clear themselves and faults that keep the boiler off until it is reset. This guide lists the common codes from Worcester's Greenstar 4000 instructions, explains the four kinds, and tells you which ones you can deal with and which need a Gas Safe engineer.
The four kinds of code
| Kind | What it means | What you do |
|---|---|---|
| Operating code | A status message during normal running | Nothing |
| Blocking fault | The heating shuts down temporarily and restarts by itself once the fault clears | Fix the cause if it is something you can see, such as low pressure |
| Locking fault | The heating shuts down and only restarts after a reset | Check the basics, reset once, call an engineer if it returns |
| Maintenance code | The boiler is flagging that it is due attention | Book it in |
Worcester's instructions describe the fault-finding information as guidance, intended for competent people. Anything that means opening the case is for a Gas Safe registered engineer.
Status messages, not faults
| Code | Worcester's description | What it means for you |
|---|---|---|
| 200 | Boiler in heating mode | Heating the radiators. Normal. |
| 201 | Boiler in hot water mode | Heating hot water. Normal. |
| 202 | Boiler in anti-cycle mode | A short pause between heat demands (five minutes by default). Normal. |
| 203 | Boiler in standby, no heat demand | Waiting for the thermostat or timer to ask for heat. Normal. |
| 204 | Current primary water temperature higher than set value | Water already hot enough; it waits for it to cool. Normal. |
| 208 | Chimney sweep demand | A test mode an engineer uses. If you see it day to day, ask your installer. |
Faults you will see most
| Code | Worcester's description | Kind | First step |
|---|---|---|---|
| 214 | Fan shut down during safety time | Locking | Reset once; if it returns, engineer |
| 224 | Maximal flue gas or heat exchanger thermostat has activated | Blocking | Check pressure and that radiators are open; persistent means engineer |
| 227 | No flame signal after ignition | Locking | Check gas and condensate, reset once. See our 227 guide. |
| 228 | Flame signal without flame present | Locking | Engineer |
| 232 | Boiler locked by external switching contact | Blocking | Worcester notes the external cut-off is not used in the UK; ask your installer |
| 233 | Boiler identification module or device electronics faulty | Locking | Engineer |
| 234 | Gas valve electrical fault | Locking | Engineer |
| 235 to 262 | Boiler electronics or system faults | Locking | Reset once; a repeat points to the control board, engineer |
Source: Greenstar 4000 installation and maintenance instructions, 6 720 891 162 (2020/09). Worcester uses different code sets on different ranges and ages of boiler, so if a code is not here, find your model's manual on Worcester's MyBosch site using the boiler's model name or GC number.
Older boilers and letter codes
Many Worcester boilers show a two-letter display code with a three-figure cause code next to it, such as EA with 227. The cause code is the useful part: it is what the engineer looks up and what you should quote when you call. Some older models signal a fault with lights as well as, or instead of, a code; on the Greenstar i, Worcester's instructions say the reset button flashes once per second and the blue mains indicator flashes. Our guide to the Worcester blue flashing light covers those.
Before you call anyone
Three checks clear a surprising share of Worcester callouts. Check the pressure is about 1 to 1.5 bar cold and top it up if it is below 1 bar. Check gas is reaching the house: does the hob light, and is there credit on a prepayment meter. In frost, check the condensate pipe outside is not frozen. Then reset once. Write down the exact code either way, because it saves time on the phone and on the visit. If you smell gas, leave the property and call 0800 111 999.
Repair or replace?
A fault that clears with one reset or a top-up costs nothing. A worn electrode or a recharged expansion vessel on a boiler a few years old is a routine repair. The sums change when the boiler is twelve to fifteen years old, the fault is a gas valve, heat exchanger or control board, or the same lockout keeps coming back. As a Worcester Bosch Accredited Installer we fit the Greenstar range from £2,000 for the Greenstar 1000 to £2,850 for the Greenstar 8000 Life, fitted, with guarantees of up to 12 years on the 8000 range (subject to Worcester's conditions). Every model and price is on our boiler prices page, and finance is available. Ask for the repair figure and the replacement figure side by side and decide with both in front of you.
Common questions
Where do I find the fault code on my Worcester boiler?
On boilers with a display, the code shows on the screen, often as a letter pair with a three-figure cause code such as EA 227. Some older models also signal a fault with lights, such as the flashing reset button and blue mains indicator on the Greenstar i.
Is code 200 or 203 a fault?
No. In Worcester's code table 200 means the boiler is in heating mode, 201 hot water mode, 202 anti-cycle mode, and 203 standby with no heat demand. They are status messages.
What is the most common Worcester fault code?
Failure to light, which Worcester's table lists as 227, no flame signal after ignition. The usual causes are no gas, a frozen condensate pipe, or worn ignition and flame sensing parts.
Can I reset any Worcester fault myself?
You can reset a locking fault once using the method in your user manual. If the same code comes back, stop: the fault needs diagnosing by a Gas Safe engineer, and repeated resets do not fix it.
Updated 18 October 2026
