How to Fix Worcester Bosch EA-338 Fault Code (Flame Loss On Ignition) UK
Worcester Bosch EA-338 means flame loss on ignition. UK diagnosis, parts to order, reset sequence.
What EA-338 means
Worcester Bosch EA-338 indicates flame loss on ignition. The boiler will lock out and refuse to fire until the fault is cleared.
Do not simply reset — EA-338 is stored in the Worcester Bosch error log and will re-trigger within minutes if the underlying part has failed.
Diagnostic sequence
Enter service mode on the Worcester Bosch boiler and read the flow/return/DHW temperatures, fan PWM, ionisation current and pump speed.
Cross-reference against the Worcester Bosch technical manual — EA-338 typically points to two or three candidate parts.
- Check wiring harness continuity to the suspect sensor before condemning it.
- Isolate at the fused spur, discharge and re-inspect connectors.
- Measure resistance / voltage at the PCB plug per Worcester Bosch test procedure.
Parts to have on the van
Carry a set of NTC sensors, an ignition electrode kit and a fan for Worcester Bosch — these three parts clear >70% of EA-338 call-outs.
Recommission
After the fix, run the Worcester Bosch boiler through a full flow test, gas rate, and combustion analysis. Log to the Benchmark book to preserve manufacturer warranty.
Frequently asked questions
- Can I reset EA-338 without changing parts?
- Only if the fault has cleared (e.g. low pressure repressurised). Persistent EA-338 means a hardware failure.
- Which is the most common cause of Worcester Bosch EA-338?
- On Worcester Bosch boilers, EA-338 most often points to the sensor or actuator matching its meaning (flame loss on ignition); check wiring and connector integrity first.
- Is a Gas Safe engineer required?
- Yes — any works past the boiler case seal require a Gas Safe registered engineer under UK law.
Browse boiler spares — 14,820 live parts.
View Boiler Spares