Error Code Diagnostics - Bosch GWH C 920 ES Instruction Manual

Error codes
8 Error codes
8.1

Error code diagnostics

To remove error code from the
i
display, press the reset button.
Display Cause
Fault in the flue gas limiter.
Temperature
(110°C) inside the cabinet.
Exhaust temperature sensor is
disconnected.
Backflow temperature sensor is
disconnected or short circuit.
Outlet temperature sensor fault
(Temperature below 36°F or above
210°F).
(Flashing) Outlet temperature sensor not
sensing
temperature.
(Status message, not an error).
Table 20
44
Solution
1. Check continuity of the flue gas limiter (see
above 230°F Go to steps two and three to determine flue gas limiter fault and
repair it.
2. Check for flue gas leakage around the top and bottom seals of
heat exchanger, use mirror to check around the rear as well as
around the viewing window.
3. Check that flue gas limiter connections are secure.
4. Unplug heater and check the wiring harness connections on the
control board.
1. Check exhaust temperature sensor connection. See
#1,
2. Check sensor (ref.
1. Check backflow temperature sensor connection. See
#1,
2. Replace backflow temperature sensor.
3. Check sensor (ref.
1. Check red wire connections at hot water temperature sensor.
Clean terminals with an eraser. If badly corroded, replace sensor
and wire harness. See
2. Sensor may trip if water temperature drops below 36°F to
protect heater from freezing conditions. Any damage due to
freezing conditions is not covered under warranty.
3. In areas where water has a high mineral content, periodic
descaling may necessary.
4. Measure sensor resistance (ref.
1. Check that the outlet temperature sensor is firmly attached to
expected output the vertical section of the hot water pipe, see
2. Ensure that outlet temperature sensor is not placed on any
bends in the hot water pipe or misreading may occur.
3. Check gas pressure. Low gas pressure may prevent the heater
from reaching desired output temperature.
4. Check supply voltage. It must be 120VAC and properly
grounded.
5. Possible defective control unit, call Bosch Water Heating for
further instructions.
page 52
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page 49
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page 52
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page 49
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Fig. 64
,
Fig. 69 page 52
,
Fig. 69
chapter 10
).
Fig. 69
chapter 10).
page 48
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page 49, chapter 10).
Fig. 75 page 59
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6 720 608 836
).
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