Worcester Bosch Boiler Not Working — Fault Codes & Fixes
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Worcester Bosch boilers are reliable workhorses in British homes, but like any heating system, they can develop faults — and when they do, a cryptic code on the front panel can feel alarming. Most faults are straightforward to diagnose once you understand what the codes mean, and many can be resolved without calling an engineer. This guide walks through the most common Worcester Bosch fault codes (EA, E9, 227, 228, E5 and others), explains what's gone wrong in plain English, and shows you what you can safely fix yourself versus when you absolutely need a Gas Safe registered engineer. If your boiler is locked out or displaying a fault code, this is the first place to look.
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Most likely cause & what to check
Worcester Bosch is the UK's most popular boiler brand — the Greenstar range (Greenstar 4000, 8000, CDi, Si, i) is found in millions of homes. If your boiler has stopped working, it will usually display a fault code on the front panel. Worcester Bosch fault codes and their meanings can be found at worcester-bosch.co.uk/support or by calling their customer service line on 0330 123 9339.
Fault code EA (ignition failure): the boiler has tried to light and failed. Press the reset button (usually marked with a flame or the word 'Reset') and hold for 3 seconds. If it locks out again within a few minutes, there may be a gas supply issue (check other gas appliances work), a faulty ignition electrode, or a problem with the gas valve — call a Gas Safe engineer.
Fault code 227 or 228 (low boiler pressure): the pressure gauge on the front of the boiler (or in the app on newer models) should read between 1–1.5 bar. If it reads below 1 bar, repressurise using the filling loop (two valves under the boiler — open until pressure reaches 1.2 bar, then close both). If pressure keeps dropping, there is a leak somewhere — call an engineer.
Fault code E9 (overheat): the boiler has reached a dangerously high temperature and shut down for safety. Do not reset repeatedly — this fault needs an engineer to investigate. Common causes include a faulty pump, blocked heat exchanger, or stuck diverter valve.
Fault code E5 (flue or fan issue): the fan that removes combustion gases may be faulty. This is a Gas Safe engineer job — do not attempt to investigate the flue yourself.
For Worcester Bosch boilers still under warranty (5 years with annual servicing, or up to 10 years on registered systems), contact Worcester Bosch directly on 0330 123 9339 — they have their own engineer network. For out-of-warranty repairs, any Gas Safe registered engineer can work on Worcester Bosch boilers and parts are widely available from Wolseley, Plumb Center, and BSS.
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Frequently asked questions
What should I do if my Worcester Bosch boiler won't ignite and shows fault code EA?
Press the reset button (usually marked with a flame) and hold it for 3 seconds — this often clears the fault temporarily. If the boiler locks out again within minutes, stop resetting it and check that other gas appliances in your home work normally; if they don't, you may have a gas supply issue. If gas appliances work fine elsewhere, the problem is likely a faulty ignition electrode or gas valve, and you'll need a Gas Safe engineer.
My boiler pressure is low and it's showing fault code 227 or 228 — can I fix this myself?
Yes, in most cases. Locate the filling loop (two small valves under the boiler) and open both slowly until the pressure gauge reads 1.2 bar, then close them both again. However, if the pressure drops again within a few days or weeks, there's a leak somewhere in the system — you'll need an engineer to find and repair it, as this won't resolve itself.
Is it safe to reset my boiler repeatedly if it keeps locking out?
No — repeatedly resetting a boiler that keeps locking out can mask a serious problem and potentially damage components. After two or three failed reset attempts, stop and call a Gas Safe engineer to diagnose the fault properly. Ignoring lockouts can lead to more expensive repairs later on.
My Worcester Bosch boiler is still under warranty — who should I contact for repairs?
Contact Worcester Bosch directly on 0330 123 9339 and they'll arrange an engineer from their own network at no cost (provided you've kept up with annual servicing). If your boiler is out of warranty, any Gas Safe registered engineer can repair it, and spare parts are readily available from plumbers' merchants like Wolseley and Plumb Center.
What does fault code E9 (overheat) mean and can I fix it?
E9 means your boiler has shut down because it's reached a dangerously high temperature — this is a safety feature. Do not keep resetting it; common causes include a faulty pump, blocked heat exchanger, or a stuck diverter valve, all of which require a Gas Safe engineer to diagnose and repair.
I smell gas near my boiler — what should I do?
Leave your home immediately, don't use any electrical switches or naked flames, and call the National Gas Emergency Service on 0800 111 999 from a safe location outside. Never attempt to investigate a potential gas leak yourself — this is a serious safety hazard.