Problem solving
67
C 950/C 1050 (Pro TL 175 C/199 C) – 6 720 805 440 (2019/10)
C6 Primary fan rotation too low in
operation.
1. Disconnect power supply cord and check wire connection on back side of fan and
the connectors on the control board, see fig. 87, page 84.
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 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.
C7 No rotational speed sensor
signal from primary fan.
1. Disconnect power supply cord and check wire connections on back side of fan and
the two connectors on the control board, see fig. 87, page 84.
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)
CA
Water flow signal over specified
maximum value.
Water flow > 10 gallon/min.
(Status message).
1. Disconnect power supply cord and check wire connections on water valve and the
two connectors on the control board, see fig. 87, page 84.
2. Excessive water pressure and flow. Ensure water pressure is less than 150psi and
flow rate is below 10 gallons per minute.
E1 Over-temperature detected by
outlet temperature sensor.
Temperature > 185°F
1. Check wire connection at hot water temperature sensor, see fig. 86, page 82.
2. In areas where water has a high mineral content, periodic descaling may be
necessary. See chapter 7.3, page 57 for directions.
3. Check sensor (ref. page 70, chapter 10).
E2 Cold water temperature sensor
fault.
1. Check connector on wires coming from top of water valve for a secure connection.
See fig. 80, page 74.
2. Sensor may trip if water temperature drops below 36°F (2°C). Protect heater from
freezing conditions as any damage due to freezing conditions is not covered under
warranty.
3. Check sensor (ref. page 71, chapter 11).
E3 Exhaust temperature sensor -
the appliance will close the
burner and lock if it gets over
194°F; (only applied for
condensing unit).
1. Clean and check heat exchanger.
2. Clean and check condensing heat exchanger.
3. Reduce maximum power (chapter 4.14, page 49).
4. Reduce water temperature.
E4 Backflow temperature sensor
over 309°F.
The appliance will close the
burner and lock (non-volatile).
1. Check inlet/outlet vent pipes.
2. Check if secondary fan connections are disconnected.
3. Check if venting specifications are met. Long vent lengths, venting with more than
three elbows, blocked vent or combination venting may cause this failure. See
chapter 4.3, page 15.
4. Call Bosch Water Heating for further instructions.
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