EA No flame detected

What the control is telling you

The burner did not light or flame was not proven within the safety time.

Applies to: Bosch Greenstar ZBR 21/28/35/42-3A boilers and ZWB 28/35/42-3A combi boilers

Likely causes

• Gas cock closed or low gas pressure
• Ground lead loose
• Damaged electrodes
• Blocked flue or condensate trap
• Gas/air ratio out of range
• Faulty gas valve
• Soiled heat exchanger
• Code plug problem

Test and repair steps

1. Warning: Disconnect mains power and close the gas cock before opening the appliance or working on the gas train.
2. Check the earth lead and the power supply.
3. Confirm the gas cock is open and measure inlet gas pressure.
4. Inspect the electrodes and replace if damaged.
5. Check the flue system and clean the condensate trap.
6. Remove and inspect the diaphragm at the fan inlet for dirt or cracks.
7. Check the gas/air ratio and the gas valve; inspect the heat exchanger for soot.
8. In room-air operation, check the combustion air openings; reseat the code plug.

Models that show this code

4 models in Bosch Greenstar

Other codes on the same units

• E9 Safety high limit or flue gas limiter tripped
• F0 Internal fault
• F1 Internal data error
• F7 Flame detected with burner off
• Ad DHW tank temperature not detected
• CC Outdoor temperature sensor not recognised
• FA Flame detected after gas shut off
• Fd Reset button pressed by mistake