Problem Solving - Bosch 940 ES Installation Manual

Problem solving

8 Problem solving
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.
Wire harness defect.
Backflow
defect - happens if sensor is
disconnected or short circuit.
Outlet temperature sensor fault
(Temperature below 36°F or above
210°F).
Table 31
* By installer or service technician only.
46
Solution
1. Check continuity of the flue gas limiter (see Fig.
above 230°F Go to steps two and three to determine air box temperature
sensor fault and replace 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 the
viewing window.
3. Check that flue gas limiter connector and spade connections
are secure.
4. Unplug heater and check the wiring harness connections inside
the control board.
1. Check wire harness, see
2. Measure resistence loose on wire harness nearby the
overmolding, must be 115 - 120 ohm.
3. Check diagnostic menu > 1P, "nC" must be showed on the
display.
temperature sensor 1. Check blackflow temperature sensor connection. See
page
2. Replace backflow temperature sensor.
3. Check sensor (ref.
1. 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.
2. In areas where water has a high mineral content, periodic
descaling may be necessary.
3. Check sensor (ref.
page 60
53
.
page 51 chapter 10
,
page 51 chapter 10
,
73 53
, page
- item 7.
Fig. 73
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