Boiler
EA 237
The EA 237 error code on a Worcester Bosch boiler indicates a flame supervision fault — the boiler is either failing to ignite or losing its flame shortly after lighting. This is a serious fault that will lock out your boiler and leave you without heating or hot water until it’s resolved.
What does this error mean?
Worcester Bosch uses the EA 237 code to signal that the boiler’s ionisation probe — the component that detects whether a flame is present — is not confirming a stable flame during or after ignition. In practical terms, the boiler tries to light, cannot verify the flame is burning correctly, and shuts itself down as a safety precaution. This is a built-in protection mechanism to prevent unburned gas from accumulating in your home.
Est. repair cost
£150–£400 for professional repair (parts + labour); replacement boiler £1,800–£3,000 installed
🔍 Likely causes
🛠️ Step-by-step fix
Step 1 — Reset the boiler: Press and hold the reset button (usually marked with a flame or ‘R’ symbol) for 3–5 seconds. Wait 2 minutes and check if the boiler fires up and runs normally. A one-off lockout can occur due to a temporary gas supply blip.
Step 2 — Check your gas supply: Confirm other gas appliances in your home (e.g. gas hob) are working. If they’re not, contact your gas supplier immediately — do not attempt to investigate the meter or pipework yourself.
Step 3 — Check the condensate pipe: In freezing weather, locate the white plastic condensate pipe (usually exits through an outside wall). If it’s frozen solid, carefully pour warm (not boiling) water over the pipe to thaw it, then reset the boiler.
Step 4 — Do not attempt further DIY: If the boiler locks out again after resetting, or if your gas hob is working fine, the fault lies inside the boiler — ignition electrodes, ionisation probe, gas valve, or PCB. These components must only be inspected and replaced by a Gas Safe registered engineer. Attempting internal boiler repairs yourself is illegal and dangerous.
Step 5 — Call a Gas Safe engineer: Book a qualified engineer and tell them the exact code (EA 237) and how many times the boiler has locked out. This helps them diagnose the fault faster and arrive with the right parts.
📞 When to call a professional
Call a Gas Safe registered engineer immediately if the boiler locks out more than once after a reset, or if you suspect a gas supply problem. Tell the engineer you have an EA 237 flame supervision lockout on a Worcester Bosch boiler — this points them directly to the ignition and flame detection circuit. Never attempt to open the boiler casing, adjust the gas valve, or tamper with any internal components yourself.
⚖️ Repair or replace?
A typical EA 237 repair — replacing electrodes, the ionisation probe, or a gas valve — costs between £150 and £400 depending on the faulty part and labour rates in your area. If your Worcester Bosch boiler is over 10–12 years old and this is not the first significant fault, replacement with a new A-rated combi boiler (typically £1,800–£3,000 installed) is worth serious consideration. For a boiler under 8 years old still within warranty, contact Worcester Bosch directly before booking an independent engineer.