Worcester Boiler Fault Codes: What They Mean and What to Do

A Worcester Bosch fault code is usually two characters, such as EA, E9, A1 or C6, shown with a three-digit number such as 227. The letters tell you what kind of fault the boiler has found and the number narrows down the cause. On Greenstar CDi boilers, EA means no flame was detected, E9 means the overheat safety circuit has tripped, A1 points to the pump running dry, usually because the system pressure is low, and C6 means the fan isn't spinning fast enough. SE and H13 are service reminders, not breakdowns. Check the gas, the pressure gauge and the condensate pipe, press reset once, and if the code comes back, book a Gas Safe engineer.

How to read the code

When a Greenstar boiler finds a fault, the display shows the code with a warning symbol and the blue light flashes. Worcester's Greenstar CDi Compact manual asks you to quote the alert code and the three-digit number under it when you report a fault, using EA and 227 as the example. The same letters with a different number can mean a different cause, so the number matters.

Before you press anything, take a photo of the whole display. A reset clears the screen, and if the code comes back later you'll want to know whether it was the same one. Also note your model name, which is on the front of the boiler or under the flap, because code meanings vary between Greenstar ranges and generations. If the blue light is flashing but you can't see a code, our guide to a Worcester boiler flashing blue light explains what that means.

Common Worcester codes explained

These meanings come from Worcester's engineer service booklet for the Greenstar CDi Classic range and the Greenstar CDi Compact user instructions. Check your own model's manual if your code isn't here or your boiler is from a different range.

Code	What Worcester says it means	What you can do
EA	Flame not detected. The boiler tried to light and failed.	Check the gas is on elsewhere and the condensate pipe isn't frozen or blocked. Reset once.
EA 227	The most common EA cause code, given as the example in Worcester's manual.	See our EA 227 guide.
E9	The safety temperature circuit has tripped (overheat).	Check the pressure and bleed any cold radiators. Reset once. If it repeats, call an engineer.
A1	The pump has run dry. The first check is system pressure below 1.2 bar.	Top up the pressure to your installer's figure and look for leaks.
C6	Fan speed too low.	Nothing for you to fix. This needs an engineer.
E2	Flow temperature sensor (NTC) defective.	Engineer only.
CC	Outside temperature sensor fault, on boilers fitted with one.	Engineer or installer.
Fd	Reset button pressed by accident.	Press reset for about 3 seconds and release. If Fd stays, call an engineer.
SE	Service reminder: the burner has run long enough to need its annual check.	Book a service. The boiler still works.
H13	Service interval reached.	Book a service. Worcester says H codes are not boiler faults.

Worcester's service booklet also sorts codes into categories. Some disable the boiler until the power is switched off and on, some until the cause is fixed, some let the boiler keep running with limited function, and some lock it out until the cause is fixed and the boiler is reset. A lockout is the one where the reset button flashes as well as the blue light. That's why a reset clears some codes straight away and does nothing for others.

Checks you can do safely

You can't open the boiler case. Only a Gas Safe registered engineer can do that. But most callouts start with one of these, and each takes a minute:

• Gas supply. Is the hob working? Does a prepayment meter have credit? Worcester's manual lists no gas or low gas pressure as the first cause of EA. If nothing gas works, contact your gas supplier. If you smell gas, leave the property and call the National Gas Emergency Service on 0800 111 999.
• Pressure gauge. Worcester's newer manuals give 1 to 1.5 bar as the normal cold pressure. If it's lower, see our guide to how to repressurise a boiler. If you keep having to top it up, there's a leak or a failing part, covered in boiler losing pressure.
• Condensate pipe. In freezing weather, a frozen condensate pipe shuts the boiler down, often with EA. Worcester says to thaw it with warm water, not boiling, and only if the pipe is at ground level. Our guide to a frozen condensate pipe or blocked flue goes through it.
• Flue. From outside, look at the flue terminal. If it's blocked by a bag, a nest or new building work, don't run the boiler. Book an engineer.
• Power and controls. If there's no code but no heat, check the fused spur, the programmer and the room thermostat before assuming a fault. Worcester notes that engineers find no boiler fault on more than 30% of service calls.

Resetting once

On a Greenstar CDi, press the reset button. Worcester's manual says "Reset" appears briefly and, if the reset worked, the boiler goes back to normal. If it didn't, the same code comes back and the blue light keeps flashing. After thawing a condensate pipe, Worcester says to hold reset for five seconds and give the boiler two to three minutes to restart. Newer Greenstar 8000 boilers are reset from the display menu instead.

Reset once, after your checks. If the same code returns, stop. Worcester is clear that some codes can't be cleared by a simple reset. Resetting again and again on an ignition or overheat lockout doesn't fix anything and can hide what's happening from the engineer. Our guide on how to reset a boiler safely covers other makes too.

Greenstar 8000 and newer displays

Newer Greenstar 8000+ boilers show faults differently. The 2024 user instructions describe a message on the display with an icon in the top right corner, coloured by how serious the fault is, and the cause shown as a number such as 232 alongside text. You reset through the menu and, if the fault persists, give the engineer the fault code and the device data.

One code on these models is a straight call to an engineer: fault 2980. Worcester's manual says not to try to fix it yourself because it could lead to a serious safety-related fault, and that heating and hot water won't be available until an engineer has sorted it.

When you need an engineer

Book a Gas Safe engineer when:

• the same code comes back after one reset,
• the code is C6, E2, CC or anything pointing at the fan, sensors, gas valve or circuit board,
• E9 keeps coming back, which suggests a circulation problem, a pump fault or a sensor,
• you need to top up the pressure more than every few weeks,
• there's any water under the boiler or a smell of gas or burning.

When you call, give the code and number, your model, what the boiler was doing when it stopped, and what you've already checked. It saves time on the day and helps the engineer bring the right parts. Worcester boilers still under the manufacturer's guarantee should go to Worcester first, because its terms say invoices from other engineers won't be accepted for guarantee work. Once the guarantee has run out, any Gas Safe engineer can work on it. Our boiler repair engineers work across London.

Repairs are charged on time: £95 an hour for labour, plus a £60 call-out that's waived when the job runs over 2 hours. Parts are extra and we confirm the price before any work starts. The pricing page has the details. For codes on other makes, start with our boiler error codes guide.

Frequently Asked Questions