6 720 644 930
Problem solving
47
(Flashing)
Outlet temperature sensor not
sensing expected output
temperature.
(Status message, not an error).
1. Check gas pressure. Low gas pressure may prevent the heater
from reaching desired output temperature.
2. Check supply voltage. It must be 120VAC and properly
grounded.
3. Possible defective control unit call Bosch Water Heating for
further instructions.
Primary fan rotation too low on
operation.
1. Disconnect power supply cord and check wire connection on
back side of primary fan and the connectors on the control board
(see Fig.
80
, page
60
).
2. Check supply voltage. It must be 120VAC and properly
grounded.
3. Check venting specifications are met. Long vent lengths,
venting with more than three elbows, blocked vent or combination
venting may cause this failure.
4. Ensure intake and exhaust terminations maintain the required
minimum clearances stated in the manual. Cross contamination
between intake and exhaust may cause the fan to alter its
rotational speed.
5. Check gas pressure. Low gas pressure may cause the fan to
change its speed to meet desired temperature.
6. Possible defective control unit call Bosch Water Heating for
further instructions.
No rotational speed sensor signal
from primary fan.
1. Disconnect power supply cord and check wire connections on
back side of primary fan and the two connectors on the control
board (see Fig.
80
, page
60
).
2. Check supply voltage. It must be 120VAC and properly
grounded.
3. Possible defective component in fan or defective control unit
call Bosch Water Heating for further instructions.
(Flashing)
Water flow signal over specified
maximum value.
Water flow > 10 gallon/min.
(Status message, not an error).
1. Disconnect power supply cord and check wire connections on
water valve and the two connectors on the control board (see
Fig.
80
, page
60
).
2. Excessive water pressure and flow. Ensure water pressure is
less than 150psi and flow rate is below 10 gallons per minute.
(Flashing)
Over-temperature detected by
outlet temperature sensor on hot
water pipe.
Temperature > 185°F
1. In areas where water has a high mineral content, periodic
descaling may be necessary. See chapter
6.3
,
page 39
for
directions.
2. Check sensor (ref.
page 51
,
chapter 10
).
Display
Cause
Solution
Table 31
* By installer or service technician only.
