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Troubleshooting
39
EA No flame ionization detected with water
flow.
(part# 8708107020)
1. Verify that all manual gas shut off valves are open.
2. Verify gas type (See Fig. 2) 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*.
6. Verify venting meets specifications outlined in
chapter
3.6. 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
required.
EC Ionization failure during operation.
(part# 8708107020)
1. Verify gas type (See Fig.
2) corresponds with the
type of gas supplied to the heater.
2. Verify the three yellow wire connections to the set
of electrodes (underside of the burner assembly)
are secure.
3. Verify that venting meets specifications per
chapter 3.6. Improper venting may cause premature
failure of the flame sensor rod.
4. Check gas pressure. See chapter
3.8*.
5. Check and adjust CO
2
readings. See
chapter
5.4.
6. Gas valve or flame sensor may be damaged. Call
Bosch Water Heating with observations and results
of previous steps.
E0 Internal hardware/software failure.
(part# 8707207239)
1. Disconnect power supply cord and check the two
wire connectors on the control board.
2. Pushing the wrong combination of buttons on the
control unit can create confusion among the
microprocessors inside. In this case, the error code
should not happen more than once or twice. Turn off
the water heater. Turn water heater back on and
reset error code. Only use the reset button ( ) to
reset any error codes.
3. Possible defective control unit call Bosch Water
Heating for further instructions.
Display Cause Solution
Table 12
* By installer or service technician only.