Worcester Bosch 219 fault code: what E9 219 means and what to do

What does the Worcester Bosch 219 fault code mean?

The Worcester Bosch 219 fault code means the safety sensor on the main heat exchanger has recorded a temperature above the safety limit, so the boiler has locked itself out and will not restart on its own. It is an overheat trip. On the Greenstar range that limit sits at around 105°C, and the lockout is the boiler stopping itself before the overheating goes any further.

You will see it written two ways, and both are right. Worcester splits the display into a fault code made of letters and numbers, E9, and a three-digit cause code, 219. The three-digit number is the one that flashes, which is why most people search for 219 on its own. In full it is E9 219, and the bare 219 and the padded E9 219 are the same fault.

Why 219 may not appear in your boiler manual

If your homeowner user guide shows E9 and nothing more, that is not unusual. The three-digit cause codes are written for the engineer rather than the householder, and the wording varies between Greenstar models, so your own model's manual is the only reliable place to check what it says for your boiler. Write the three digits down anyway, because quoting them when you book saves a diagnostic step.

What 219 does not tell you

219 is a temperature reading, not a verdict on any single part. It records that the sensor on the main heat exchanger measured a temperature above the safety limit. Most of the time the heat exchanger itself is sound and the real problem is that water is not moving through it fast enough to carry the heat away, which is why sludge, limescale and a tired pump come up so often.

Key facts

The quick version, before the detail.

• Meaning: the maximum safety sensor on the main heat exchanger has recorded a temperature above the safety limit, which on the Greenstar range sits at around 105°C.
• Usually shown as E9 219. E9 is the fault code, 219 is the flashing three-digit cause code, and both point at the same fault.
• It is a locking error. The boiler stops and will not restart on its own.
• The component involved is the maximum safety sensor on the main heat exchanger, inside the casing and engineer-only.
• Not every Greenstar model uses the three-digit cause codes, and the wording varies between ranges, so check your own model's manual.
• 219 is not 220, 221 or 224. Those sit near it on the same code list and point at different things.
• The usual reason is poor circulation rather than a failed heat exchanger: sludge, limescale, a weak or seized pump, or a closed valve.
• DIY scope: read the pressure gauge with the system cold, then look and listen. Nothing behind the case, and one reset at most, because an overheat lockout is not one to sit resetting.

What causes the 219 fault?

The reading is one thing and the reason is another. 219 tells you the temperature at the safety sensor went above the limit. Nearly always that is because heat is going into the water faster than the water can carry it away, so the temperature at the sensor spikes and the lockout does its job.

In real homes, engineers most often find magnetite sludge or limescale narrowing the heat exchanger and radiators, a weak, airlocked or seized pump, heating valves closed or partly closed, a stuck diverter valve, low system pressure, an air lock, or a safety sensor that has drifted and reports a temperature that is not really there. In hard-water areas limescale is the usual culprit. Those are the likely causes, not the definition of the code.

219, 220, 221 and 224 are not the same fault

These four sit close together on the same code list and get blurred together on third-party code pages. 219 is a temperature above the limit from a sensor that is still electrically healthy, which can be a genuine overheat or a sensor that has drifted. 220 and 221 point at the sensor or its wiring failing outright. 224 is a different overheat device again, and on ranges such as the Greenstar 8000 it is the code you see instead.

Telling an engineer the exact three digits, rather than just that the display says E9, saves a diagnostic step.

219 causes and what happens next

What can you safely check yourself?

Two checks are worth doing before you call anyone, and neither of them involves removing a panel.

1. Read the pressure gauge with the system cold. It should sit at around 1.0 to 1.5 bar cold, and it rises once the heating has been running. Check the target printed on your own gauge or in your manual, because Worcester quotes slightly different figures across the Greenstar ranges. If it reads low, re-pressurise using the integral filling link as your manual describes, then remove the filling key or disconnect the external filling loop afterwards, which is a water regulations requirement.

2. Look and listen, with the case left alone. Radiators cold at the bottom or in patches, kettling or banging, valves turned off, and damp or staining around the boiler and pipework all point at circulation. Note what you find, because it gives an engineer a head start.

What not to do is sit there clearing the lockout. Try one reset and no more: the lockout is the safety device doing its job, and clearing it again and again forces a boiler that is genuinely running too hot to keep firing in that state. If 219 comes straight back, book a Gas Safe registered engineer rather than resetting your way through it.

Everything else on this code is engineer work: removing the case, reading the safety sensor temperature, resistance-testing the sensor and its wiring, replacing the sensor, testing the pump, clearing debris from the heat exchanger, flushing the system, checking the diverter valve, and checking the gas side.

When to call an engineer

Call as soon as 219 shows, and without hesitating if it keeps coming back, if it shows with the boiler cold, if the pressure keeps falling, or if you can hear kettling. An overheat lockout that returns is a fault that will not clear itself.

One safety note first. Work on the gas side of a Worcester Bosch boiler is for a Gas Safe registered engineer, and it is unsafe and illegal to attempt it yourself. If you smell gas, or a carbon monoxide alarm sounds, stop using the boiler, get everyone out of the building and call the National Gas Emergency Service on 0800 111 999. If your boiler runs on LPG, call the supplier's number on the side of the gas tank instead.

You can book a one-off repair with us, or call us on 0333 772 6247. One-off repair visits run Monday to Friday, 09:00 to 17:00. We work with a national network of thousands of Gas Safe registered engineers, and we aim to get an engineer out to you within two working days, with cover-plan call-outs running Monday to Friday, 08:00 to 18:00, unless it is a genuine emergency breakdown. A £95 call-out fee, paid in advance, covers the engineer coming out and diagnosing the fault. Any parts and further labour are quoted separately and explained to you before the work goes ahead, and one-off repairs do not carry a workmanship guarantee.

If you would rather not meet a bill like this out of the blue next time, a Smart Plan boiler and central heating module is worth a look, with one thing said up front. Cover is for future breakdowns rather than a fault your boiler is already showing, so a plan set up tonight would not pay for tonight's 219. For that, book a one-off repair.

The module covers parts and labour up to £500 in any 12-month period if your boiler is under 7 years old, or up to £200 if it is over 7. Those are caps, not a promise the whole repair is paid for. A job like a system flush or a new pump can cost more than the cap, and anything above your cover limit is down to you.

The rest of the terms, so you have them before you decide. Cover-plan call-outs run Monday to Friday, 08:00 to 18:00, unless it is a genuine emergency breakdown as set out in your terms, so a fault reported on a Friday evening can wait until Monday. A £95 call-out fee, paid in advance, applies in your first 30 days, when cover still applies, for faults the plan does not cover, if the engineer cannot get access, and for early annual-service requests. Using a module starts a 12-month agreement period from the first time you use a service. There is a 14-day cooling-off period, but it ends the moment a service is carried out, and leaving early after that costs the remaining months or 75% of the outstanding balance. Smart Plan is a service plan, not insurance, so it funds covered repairs up to the limits in your terms rather than paying a cash sum.

Worcester Bosch 219 fault code FAQs

Seeing 219 on your Worcester Bosch?

Book a one-off repair, Monday to Friday, 09:00 to 17:00, and a Gas Safe registered engineer can test the safety sensor, the pump and the circulation. We aim to get an engineer out to you within two working days, with cover-plan call-outs running Monday to Friday, 08:00 to 18:00, unless it is a genuine emergency breakdown. A £95 call-out fee, paid in advance, covers the visit and the diagnosis, any parts and further labour are quoted separately, and one-off repairs carry no workmanship guarantee. Cover is a separate thing, and it is for future breakdowns rather than a fault already on your display, so a module set up tonight would not pay for tonight's 219. It funds covered repairs up to your cover limit rather than paying a cash sum, £500 in any 12-month period if the boiler is under 7 years old or £200 if it is over 7, and those are caps rather than a promise the whole repair is paid for. A £95 call-out fee, paid in advance, also applies in your first 30 days, when cover still applies, for faults the plan does not cover, no-access visits and early annual-service requests. Using a module starts a 12-month agreement period from the first time you use a service, there is a 14-day cooling-off period that ends the moment a service is carried out, and leaving early after that costs the remaining months or 75% of the outstanding balance. It is a service plan, not insurance. Call 0333 772 6247 if you would rather talk it through.

Helpful links

• Worcester Bosch E9 fault code
• All Worcester Bosch fault codes
• Worcester Bosch H07 low pressure
• Worcester Bosch EA / 227 fault
• Worcester Bosch A1 fault code
• Boiler repair
• Boiler & central heating cover
• More boiler guides on the blog
• Check an engineer on the Gas Safe Register
• Worcester Bosch (official site)
• Gas safety in the home (HSE)