Worcester Bosch EA Error: Flame Detection Lockout
Resolve Worcester Bosch EA error code (flame not detected).
Flame sensing failure. The control board attempted 4 ignition trials without sensing a stable flame ionization microamp signal, initiating safety lockout.
Probable Causes
Frozen or obstructed external condensate discharge pipe causing acidic water to flood the burner.
Soot or oxidation buildup on the flame sensing electrode rod.
Insufficient dynamic gas working pressure (below 18 mbar natural gas).
Diagnostic & Testing Steps
- •Blue operational light flashes rapidly accompanied by EA code on LCD.
- •Audible sparking sounds occur 4 times followed by total shutdown.
- •Complete lack of hot water and central heating.
Tools & Equipment Required
- ✓Torx T20 & 4mm Hex KeyRemove outer casing and unfasten sealed combustion chamber hood.
- ✓Brass Wire Cleaning BrushRemove silica and carbon deposits from flame sensing electrode rod.
- ✓Condensate Siphon Pipe PliersInspect, flush, and unclog transparent condensate trap and discharge pipe.
- ✓Warm Water Pitcher & TowelsPour warm water along frozen exterior condensate pipe run to dissolve ice blockages.
- ✓Inspection FlashlightInspect burner ceramic insulation and electrode spark gap alignment.
Fast Reset Sequence: Worcester Bosch / Bosch Boiler Lockout Reset
Before unmounting panels or beginning diagnostic procedures, attempt this manufacturer reset to clear transient microcomputer lockouts:
- 1.Press and hold the Reset button on the control fascia for 3 to 5 seconds.
- 2.Verify system water pressure gauge reads between 1.2 and 1.5 bar in the green zone.
- 3.Allow 2 minutes for the ignition sequence and spark electrode to attempt flame detection.
- 1
Step 1: Inspect and Thaw Condensate Drain
[ ] DoneExamine external plastic condensate pipe for freezing during winter months. Pour warm (not boiling) water along pipe exterior.
Verification:Condensate drains freely and internal siphon trap is emptied of excess water. - 2
Step 2: Clean Flame Sensing Ionization Electrode
[ ] DoneDisconnect electrode lead, unbolt retaining bracket, and polish metal probe to remove non-conductive oxide film.
Verification:Ceramic insulator is intact with zero micro-cracks; spark gap set to 3.5 mm. - 3
Step 3: Execute Reset Sequence on Board
[ ] DonePress and hold the Reset button for 3 seconds until the blue light stops flashing and display returns to standby.
Verification:Burner ignites cleanly on first spark and flame indicator illuminates steadily.
Repair Solutions
Thaw external condensate pipe with warm water and clear internal siphon blockage.
Clean flame sensing electrode probe with fine Scotch-Brite pad.
Measure gas inlet pressure at the gas valve test nipple under full burner load.
Frequently Asked Questions
Why does Worcester EA error occur mostly during freezing weather?
Over 80% of winter EA callouts are caused by frozen external condensate pipes backing water into the burner chamber.
How do I test the flame sensor with a multimeter?
Connect multimeter in series (DC microamp mode) with the flame probe lead. A reading above 1.8 µA confirms a healthy ionization circuit.