Error code ea - Bosch AquaStar 2400ES-NG

Error code EA - No sparks for the electrodes
The ionization electrodes are not making sparks when water is flowing. There are many reasons for this problem and here are some; low gas pressure, fan speed is low, wire connections are loose, the air in the gas line, no gas.

Copy following links to narrow down cause for EA error code:
http://waterheatertimer.org/pdf/Bosch_EA_error_code_troubleshooting.pdf
http://waterheatertimer.org/Troubleshoot-Bosch-Tankless-water-heater.html

If you need further help, I’m available over the phone at https://www.6ya.com/expert/gene_9f0ef4df2f9897e7

Before calling service technician, open following links for Bosch error codes, and contact information, and possible product manual for your model, etc:
http://waterheatertimer.org/Troubleshoot-Bosch-Tankless-water-heater.html
http://waterheatertimer.org/pdf/Bosch_EA_error_code_troubleshooting.pdf
http://waterheatertimer.org/pdf/Bosch-GWH2400ES-error-codes.pdf
http://waterheatertimer.org/pdf/Bosch_A4-E4_error_code_troubleshooting.pdf

Error code AE is not shown, but error EA means "burner flame not recognized by control unit when water is flowing"

There is also error A3 and A3 E3: jumper connection is not correct

Before calling service technician, open following links for Bosch error codes, and contact information, and possible product manual for your model, etc:
http://waterheatertimer.org/Troubleshoot-Bosch-Tankless-water-heater.html
http://waterheatertimer.org/pdf/Bosch_EA_error_code_troubleshooting.pdf
http://waterheatertimer.org/pdf/Bosch-GWH2400ES-error-codes.pdf
http://waterheatertimer.org/pdf/Bosch_A4-E4_error_code_troubleshooting.pdf

Error code AE is not shown, but error EA means "burner flame not recognized by control unit when water is flowing"

There is also error A3 and A3 E3: jumper connection is not correct

Before calling service technician, open following links for troubleshoot resources including common error codes, Bosch contact information, link to service manuals, and possible product manual
http://waterheatertimer.org/Troubleshoot-Bosch-Tankless-water-heater.html
http://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'

1. Verify that all manual gas shut off valves are open.
   
2. Check gas type.
   
3. 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.
   
4. Check three wire connections to ignition group on the lower front of the heat exchanger are secure.
   
5. Check gas pressure.
   
6. Check venting specifications are met. Improper venting may cause premature failure of the flame sensor rod.
   
7. Check that the minimum power fan speed has been adjusted to the proper value.
   
8. 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 pressure.

http://www.digelair.net/pdfs/TECHLIT/BOSCH/MANUALS/Bosch-ProTankless_AM.pdf
http://www.bosch-climate.us/files/201009031238250.GWH715ES_English_12.2008.pdf

Above are the manuals required to diagnose and service your error code.

EA: 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 pressure.

http://www.tankless-water-heaters.com/troubleshooting.htm

1. Verify that all manual gas shut off valves are open.
   
2. Verify gas type (See Fig. 2 in installation manual) corresponds with the type of gas supplied to the heater.
   
3. Reset error code and open a water tap to cycle the heater in an effort to purge air from gas line (especially 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.
   
4. Verify the three yellow wire connections to the set of electrodes (underside of the burner assembly) are secure.
   
5. Verify gas pressure meets specifications outlined in chapter 3.8. See Bulletin TWH-G2-03.
   
6. Verify venting meets specifications outlined in chapter 3.6 of the installation manual. Improper venting may cause premature failure of the flame sensor rod.
   
7. 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 not, Call Bosch Water Heating with observations. Readings from above gas pressure test will be req

http://www.boschhotwater.com/HelpfulResources/TechnicalSupport/BoschAquaStarModels/250SXTechSupport/Troubleshoot/tabid/563/Default.aspx

There are three electrodes (connected next to each other by a single piece of metal) that run up into the heat exchanger. They are situated behind the black plastic air intake in the lower half of the unit. Pull out the electrodes and clean them off with steel wool or fine sand paper. Also take the opportunity to blow the dust out of the inside of the unit and clean out the air intake.

Think maybe just loose connect to me.