Overview
EA 234 on a Worcester Bosch GB162 means the boiler control has detected an interruption to the gas valve contacts or coil – in other words the controller is not seeing the expected electrical connection or signal to the gas valve. The gas valve is the device that allows gas to flow to the burner when the electronics call for ignition; if the valve coils or their wiring are disconnected or open circuit the boiler will not establish or maintain a flame and will lock out with an EA fault. This is a significant fault. It will usually present as a lockout (no heating or hot water) and is potentially a gas safety related issue if it is caused by a valve fault or wiring problem. Because the fault involves ignition and gas control components it is not a routine DIY repair. Some basic, non-intrusive checks can be done safely by a homeowner (see troubleshooting), but any internal electrical checks, gas valve replacement or wiring repairs must be carried out by a Gas Safe registered engineer.
Possible Cause: The contacts of the gas valve have been interrupted.
Troubleshooting Steps
Safety precautions:
- If you smell gas, leave the property immediately, do not operate switches or use phones inside, and call the gas emergency number for your area. Do not attempt any checks.
- If you are not competent with electrical or gas appliances do not open the boiler casing or probe internal components. Working on the gas valve, wiring, ignition or PCB requires a Gas Safe engineer.
- Do not repeatedly reset the boiler if the fault returns; frequent resets can mask a dangerous condition and waste time for the engineer.
Initial checks a homeowner can do (non-intrusive):
- Note the fault exactly (EA 234) and any flashing cause code or triangle icon. Press the spanner/return button if your model shows a cause code to capture additional info for the engineer.
- Try a single reset: follow the manual for your GB162 (press reset or hold the reset point for 3 seconds). Wait at least 30 seconds after the lockout before attempting one reset. If the fault returns immediately or repeatedly, stop attempting further resets.
- Check the boiler has mains power: ensure the fused spur or isolator and the household fuse box haven’t tripped. Check the boiler display/backlight is on.
- Check gas supply to the property: try another gas appliance (hob) or check the gas meter if safe to do so. Make sure the isolation valve at the gas meter/boiler is open. If multiple appliances have no gas, contact your gas supplier.
- Inspect the external flue terminal and condensate outlet for obvious blockages or heavy debris and check for a frozen condensate pipe if temperatures are low (EA 227 is more common for frozen condensate but a blocked flue can cause ignition/ionisation faults).
What the EA 234 usually indicates and what a Gas Safe engineer will check/diagnose:
- The code points to the gas valve coil/contacts being open or disconnected, or the control electronics not energising the valve. Possible causes: a loose or disconnected low-voltage connector to the valve, a broken wiring loom, an internal coil failure in the gas valve, a failed relay or driver on the control PCB, water ingress or corrosion at the connector, or a previous DIY/servicing disturbance.
- A professional will isolate the boiler, remove the casing, visually inspect the gas valve connector and wiring for damage or corrosion, check connector seating, and test coil resistance and continuity with a multimeter to confirm an open circuit or short. They will also test the PCB output when calling for gas (measuring the drive voltage to the valve) to establish if the electronics or the valve is faulty.
- If the valve coils are open or the coil is internally failed the valve assembly will usually need replacement. If the PCB is not driving the valve correctly the control board or wiring may need repair or replacement. The engineer will also perform leak tests and a full safety check after any repair.
Safe diagnostic/fix steps homeowners should not perform but should expect from the engineer:
- Isolation of mains and gas, removal of the boiler casing, examination of the gas valve connector, and measurement of coil resistance and continuity.
- Verification of the PCB output signal to the gas valve during an ignition attempt and inspection for any burnt or loose terminals on the control board.
- Replacement of the gas valve or PCB if faulty, followed by gas tightness testing, commissioning and a safety check.
Final advice and when to call a professional:
- Because EA 234 involves gas control and ignition systems, a Gas Safe registered engineer must carry out internal checks and repairs. Contact a Gas Safe engineer and provide them the exact error code (EA 234) and any other cause code or symptoms you observed. If you have any sign of gas smell, immediate evacuation and a gas emergency call are required. Do not attempt to replace the gas valve, test live circuits, or make permanent wiring repairs yourself.
Helpful Resources
Boiler Manual
Download the official PDF manual for the Worcester Bosch GB162 Boiler.