Troubleshooting
51
Condens 8300i W – 6721841531 (2022/10)
232 B Boiler locked by external switching contact 1. Connect the plug for the external switching contact.
2. Install jumper/check condensate pump according to manufacturer's specifications.
3. Adapt switching point of the external temperature switch to the system.
4. Replace connecting lead to the external temperature switch.
5. Replace external temperature switch.
233 V Boiler identification module or device
electronics faulty
1. Install boiler identification module/coding plug.
2. Connect plug to boiler identification module/coding plug.
3. Replace boiler identification module/coding plug (Bosch contact customer service).
234 V Gas valve electrical fault 1. Replace connecting lead and reset once replacement is complete.
2. Replace air/gas ratio control valve and reset once replacement is complete.
235 V Conflicting versions of boiler electr. and
boiler identification
1. Check boiler identification module/coding plug.
2. Install valid combination of control device/burner control unit.
237 V System fault 1. Replace boiler identification module/coding plug (Bosch contact customer service).
2. Replace control device/burner control unit.
238 V Boiler electronics faulty Replace control device.
242 -
263
V System fault boiler electronics / basic
controller
1. Remedy contact problem.
2. If necessary, replace control device or boiler identification module/coding plug (Bosch
contact customer service).
265 B Heat demand lower than energy supplied –
268 O Relay test was activated –
269 V Flame monitoring Replace control device/burner control unit.
273 B Operation of burner and fan interrupted –
281 B Pump stuck or running in air 1. Check whether the pump is blocked, unblock or replace if necessary.
2. Ensure that the heating water can circulate correctly.
3. Vent the pump.
306 V Flame signal after closing the fuel supply 1. Replace the air/gas ratio control valve.
2. Replace the ionisation cable.
3. Replace the control device/burner control unit.
358 O Anti-seizing functn. active –
360 V System fault boiler electronics / basic
controller
1. Install boiler identification module/coding plug.
2. Connect plug to boiler identification module/coding plug.
3. Replace boiler identification module/coding plug (Bosch contact customer service).
362 V Boiler identification module or boiler
electronics faulty
Replace boiler identification module/coding plug (Bosch contact customer service).
363 V System fault boiler electronics / basic
controller
Replace control device/burner control unit.
815 W Low loss header temp. sensor faulty 1. Check hydraulic configuration, correct if necessary.
2. Check sensor for breaks or short circuits, replace if necessary.
1010 O No communication via EMS BUS connection 1. Rectify wiring fault and switch the control unit off and on again.
2. Repair the BUS cable or replace it.
3. Replace faulty EMS-BUS node.
1013 W Max. combustion point reached 1. Carry out maintenance.
2. Reset service display.
1017 W System pressure too low 1. Top up water and vent the system.
2. Check the pressure sensor, replace if necessary.
1018 W Maintenance interval expired 1. Carry out maintenance.
2. Reset service display.
1019 W Incorrect pump type detected 1. Check pump cabling.
2. Check that the correct heating pump type is in the appliance, replace if necessary.
1021 W Cylinder charging or hot water temperature
sensor faulty
1. Connect the plug to the temperature sensor correctly.
2. Connect the plug to the control device correctly.
3. Attach the temperature sensor correctly.
4. Check the temperature sensor, replace if necessary.
5. Check temperature sensor connecting lead, replace if necessary.
1023 Maximum run time including standby time
reached
1. Carry out maintenance.
2. Reset service display.
Fault
code
Fault
category
Fault text on the display, description Remedy
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