Before calling service technician, open following links for troubleshoot resources including common error codes, Bosch contact information, link to service manuals, and possible product manualhttp://waterheatertimer.org/Troubleshoot-Bosch-Tankless-water-heater.htmlhttp://www.boschhotwater.com/HelpfulResources/TechnicalSupport/BoschAquaStarModels/2400ESTechSupport/Troubleshooting/tabid/1295/Default.aspx
Call Bosch 800-642-3111
Multiple error codes can mean PC board failure.
AF might be A9, but not sure.
EA is 'no flame ionization detected with water flow'
- Verify that all manual gas shut off valves are open.
- Check gas type.
- Reset error code and open a water tap to cycle the heater in an
effort to purge air on new installations. Cycling hot water tap on
and off multiple times may be necessary. If heater still faults with
EA error code, have a licensed gas technician properly purge air
out of the gas line leading to the water heater.
- Check three wire connections to ignition group on the lower
front of the heat exchanger are secure.
- Check gas pressure.
- Check venting specifications are met. Improper venting may
cause premature failure of the flame sensor rod.
- Check that the minimum power fan speed has been adjusted to
the proper value.
- Observe inside the viewing window of the heat exchanger when
a hot water tap is opened. Sparking should be followed by a
steady blue flame. If flame is unstable or yellow with proper gas