Faults That Are Shown On The Display - Bosch Greenstar Series Installation And Service Instructions For Contractors

Faults
17.2

Faults that are shown on the display

Display Description
A7 DHW temperature sensor defective.
A8 Communication fault.
Ad DHW tank temperature not detected.
The DHW tank temperature sensor was recognized
before the connection was lost.
b1 Code plug not detected.
b2/b3/b4/ Internal data error.
b5/b6
b7 Fault in the burner controls.
C6 Fan not running.
CC Outdoor temperature sensor not recognized.
d3 Temperature high limit defective.
External guard has tripped.
Temperature limiter locked out.
d5 External supply temperature sensor defective (low-loss
header).
The external supply temperature sensor was recognized
on the BUS and then reconnected to the appropriate
terminal.
E2 Supply temperature sensor defective.
E3 Additional supply temperature sensor defective.
E9 Heat exchanger safety high limit or flue gas temperature
limiter has tripped.
74
Elimination
▶ Check temperature sensor and leads for interruptions or shorts, and
replace if defective.
▶ Insert code plug correctly; replace if defective.
▶ Check BUS communications wiring, replace if defective.
▶ Check control, replace if defective.
▶ Check DHW tank temperature sensor and connecting lead, replace if
defective.
▶ Reset the boiler to the factory default settings ( service function 8.E).
▶ Insert code plug correctly; replace if defective.
▶ Reset boiler to the factory default setting ( service function 8.E).
▶ Reset boiler to factory to default setting ( service function 8.E).
▶ Check fan leads and fan, replace if defective.
▶ Check outdoor temperature sensor and leads for interruptions, replace if
defective.
▶ Verify the outdoor temperature sensor is connected to terminals A and F.
▶ Check temperature sensor and leads for interruptions or shorts, and
replace if defective.
▶ Temperature guard TB1 has tripped. Check if jumper across 8-9 or PR-P0
is missing.
▶ Reset external temperature limiter (if installed).Reset LWCO (if installed).
▶ Reset pressure regulator (if installed).
▶ Check temperature sensor and leads for interruptions or shorts, and
replace if defective.
▶ Check whether only one temperature sensor is connected; otherwise
remove second temperature sensor.
▶ Reset the boiler to the factory default settings ( service function 8.E).
▶ Check temperature sensor and leads for interruptions or shorts, and
replace if defective.
▶ Check temperature sensor and leads for interruptions or shorts, and
replace if defective.
▶ Check flue gas safety high limit and leads for interruptions or shorts, and
replace if defective.
▶ Check heat exchanger safety high limit and leads for interruptions or shorts,
and replace if defective.
▶ Check the operating pressure.
▶ Check temperature limit; replace if defective.
▶ Check pump capacitor; replace pump if defective.
▶ Check PCB fuse, replace if blown (6.3 A fuse according to IEC default).
▶ Purge the appliance.
▶ Check heat exchanger on the DHW side; replace if clogged.
Greenstar – 6721822579 (2021/01)