Bosch 250 SXO LP User Manual page 21

Display Cause
E9 Temperature limiter opened circuit (overheat).
Trips at 220F (104C).
EA No ionization during safety time (safety time out).
Note: appliance makes 3 ignition attempts
before entering error mode "EA".
EC The ionization signal momentarily disappeared
more then 5 times in less then 30 seconds. CO
may be out of adjustment
FA Leakage error (gas valves do not close gas
circuit).
F7 Ionization error (flame sensing at stand-by).
E0 Internal software/hardware failure.
A7 Hot water temperature sensor/receiver defect
(from control unit).
A9 Hot water temperature sensor/receiver mis-
(flashing) assembled (from control unit).
Note: if display shows "A9" flashing, the
appliance can be operated normally, but
performance may be affected.
C1 FAN rotation too low at start-up (from control
unit).
C6 FAN rotation too low at operation (from control
unit).
C7 No rotational speed sensor signal from FAN
CA Water flow signal over specified maximum value
E2 Inlet temperature sensor fault
A2 Overheat protection fault
Table 5
* By installer or service technician only.
6 720 607 440
Solution
Check connections. *
Check heat exchanger condition.*
Check gas pressure.
Check that gas is not diluted with air, as a
result from recent gas pipeline rework.*.
Check if vent terminal is blocked (especially
when the appliance starts up for some sec-
onds and then looses ionization signal).*
Check ionization electrode.*
2
Check for a proper ground.*
Check CO levels.* (see chapter 9)
2
Check gas valve and control unit.*
Check control unit.*
Check control unit.*
Check water temperature sensor/receiver and
connections.*
Check incoming water temperature to heater, it
must be above 32°F (0°C)
Check that the water temperature sensor/receiver is
properly assembled on the horizontal of the hot
water pipe.*
Check that the water temperature sensor/receiver is
free from corrosion or moisture.*
Check supply voltage.*
Check fan and connections.*
Check control unit.*
Check if vent terminal is blocked.*
Check supply voltage.*
Check fan and connections.*
Check control unit.*
Check fan and connections.*
Check control unit.*
Check water valve and flow sensor.*
Check water temperature sensor/receiver and
connections.*
Check incoming water temperature to heater, it
must be above 32°F (0°C)
Check connections to the overheat protection.*
Check sensor continuity.*
Check heat exchanger sealings and walls.*
Troubleshooting
2.9 *
(see chapter )
21