🔥 Worcester Greenstar Ignition / Ionisation Fault: What's Going On and How to Fix It

If your Worcester Bosch Greenstar has stopped firing up and you're staring at an EA, E9 or "ignition lockout" message on the display, you're not alone. It's one of the most common faults we get called out to across Nuneaton, Coventry and the wider Midlands, especially after a cold snap or a long summer where the boiler hasn't run for months.

The good news: it's usually fixable, and a fair chunk of the time you can clear it yourself in five minutes. The bad news: if a reset doesn't sort it, the cause is almost always one of three components, and getting at them properly means a Gas Safe engineer.

Here's what an ignition or ionisation fault actually means, what to check first, and when to put the screwdriver down and pick up the phone.

What an Ignition / Ionisation Fault Actually Means

Worcester Greenstars use a flame ionisation rod (sometimes called a flame sense electrode) to confirm the burner has actually lit. The control board sends a tiny electrical signal through the flame, and if it reads back current, the boiler knows the gas has ignited and it's safe to keep gas flowing.

If the board sends gas + a spark and gets no signal back within a few seconds, it cuts the gas, locks the boiler out, and throws an error. On most Greenstar 25i, 30i, 8000 Life and Style models that's an EA, E9, or 227 code depending on the firmware.

So when the boiler says "ignition fault", it's really saying one of three things:

1. I tried to light the burner and nothing happened.
2. I lit the burner but the flame went out almost immediately.
3. The burner is lit but I can't sense the flame, so I'm shutting down to be safe.

Each of those has a different root cause. The fix depends on which one you're dealing with.

Step 1: Read the Code Properly

Before you do anything else, look at the display and write the exact code down. Greenstar codes that point to ignition or ionisation include:

• EA / 227, no flame detected after ignition attempt (most common)
• E9, flame detected when there shouldn't be one (stuck signal)
• D1 / 224, flame loss during operation
• A1 / 281, pump or flow issue causing ignition to abort (often misdiagnosed as ignition)

Take a photo of the display. If you end up calling us, that single photo can save 20 minutes of diagnosis.

Step 2: Check the Obvious Stuff First

Is there gas to the boiler?

Sounds silly, but it's the number one cause of phantom "ignition faults". Check:

• Other gas appliances in the house. If the hob and gas fire are out too, your supply is off. Check the meter and any emergency control valve.
• If you're on a smart meter and you've topped up recently, sometimes the supply needs a manual reset on the meter itself. Hold the A button until "call for credit" disappears.
• If you've had work done outside, a contractor may have closed the gas service valve. The lever near the boiler should be in line with the pipe (open), not across it (closed).

Is the condensate pipe frozen?

This is the silent killer of Greenstars between November and February. The condensate pipe is the white plastic pipe that runs from the bottom of the boiler to an outside drain. If it freezes, the boiler can't expel waste water, fills up internally, and locks out, often showing as an ignition or pressure fault rather than a condensate one.

Symptoms:

• Boiler was working yesterday, now won't fire after a cold night.
• You can hear a gurgling or bubbling sound near the bottom of the boiler.
• The pipe outside feels cold and rigid, sometimes with frost on it.

Fix: pour warm (not boiling) water along the outside of the pipe, or wrap a microwaved hot water bottle around it for ten minutes. Then reset the boiler. If it fires up, you've found your culprit. Lag the pipe before next winter.

What's the pressure?

Greenstars need at least 1 bar to ignite. If your gauge is sitting below that, fill via the filling loop until it reads 1.2 to 1.5 bar (cold), then reset. If the pressure won't hold, you have a leak somewhere and that's an engineer job.

Step 3: Try a Proper Reset

A "proper" reset is more than just pressing the reset button. The control board can latch faults and just resetting won't always clear them.

1. Press and hold the reset button (the one with the flame icon) for around 5 seconds until you hear the boiler click.
2. If that doesn't work, switch the boiler off at the fused spur (the switch on the wall next to it). Wait a full 60 seconds. Switch back on.
3. Turn the heating up so the boiler has to fire. Listen carefully. You should hear: fan ramp up, click click click of the spark, then a soft whoosh as it lights.

If you hear the spark but no whoosh, it's not getting gas or it's not sensing flame. If you hear nothing at all, it's an electrical or fan issue and we're past DIY territory.

Step 4: When the Reset Doesn't Hold

If the boiler fires, runs for 30 seconds and then locks out again, you've almost certainly got one of the following. None are DIY fixes on a sealed gas appliance, but knowing the cause helps you understand the bill.

Dirty or corroded ionisation electrode

This is the cheapest, most common fix on a Greenstar with an EA fault. The flame sense rod sits over the burner and gets coated with a dark scaly residue over time, especially in hard water areas like Nuneaton and Coventry. Once the coating builds up enough, the electrode can't read the flame current, and the boiler shuts down even though the burner is lit perfectly.

Fix: an engineer removes the electrode, gently cleans it with fine wire wool or a dedicated electrode cleaner, checks the gap, and refits. 20 minute job. We fix this one almost every week.

Faulty spark electrode or HT lead

If the boiler isn't even attempting to light (no clicking sound), the spark electrode or its high-tension lead has failed. Worcester's spark electrodes are a known wear part on the 25i and 30i models, and many that we replace are between 7 and 10 years old.

Fix: replace the electrode and lead together. Around an hour on the bench.

Gas valve issue

If the spark is firing and the electrode is clean, but the boiler still won't ignite, the gas valve isn't opening. This is usually electrical (a failed solenoid coil) rather than mechanical, and it shows up as a clean spark with no whoosh.

Fix: replace the gas valve. Worcester valves are not cheap, but they're a permanent fix.

PCB / control board fault

Rarer, but it does happen. If the board can't deliver consistent voltage to the spark generator, ignition becomes intermittent. Symptoms: works when cold, fails when warm, or vice versa. The fix is a new PCB. We always rule out the cheaper components first.

What It Costs to Fix

A rough guide based on what we charge in the Nuneaton and Coventry area:

• Electrode clean: typically £95 to £130, parts and labour, same visit.
• Spark or flame sense electrode replacement: £140 to £180.
• Gas valve replacement: £350 to £480 depending on model.
• PCB replacement: £400 to £550.

If your boiler is over 12 years old and the bill comes back over £500, it's worth at least asking whether replacement makes more sense than repair. We'll always tell you straight.

How to Stop It Happening Again

• Get the boiler serviced annually. Electrode cleaning is part of a proper service, and most ignition faults we see are on boilers that have skipped a year or two.
• Lag the condensate pipe before winter, especially if it runs along an outside wall.
• Don't ignore early warning signs. A boiler that needs the reset button pressed once a week is telling you something.

Key Takeaways

• EA, E9 and 227 codes on a Worcester Greenstar all point at the ignition or flame sense system.
• Check the obvious first: gas supply, frozen condensate pipe, low pressure.
• A proper power-cycle reset clears latched faults that the reset button alone won't.
• If it locks out repeatedly, the cause is usually a dirty flame sense electrode, a worn spark electrode, or (less often) a gas valve.
• An annual service catches most of these before they leave you without heat.