Viessmann B0KA - Page 61

61
Displayed fault
code
System characteristics Cause Measures
78 Normal operation Communication between
heat management unit
and programming unit dis-
rupted/interrupted.
Check cables and plug-in connec-
tions between central control unit
and programming unit.
Check cables for correct routing/
position.
87 Burner locked out. Internal
pump off. No central heating
and no DHW heating.
System pressure too high Check the system pressure. Cor-
rect if necessary.
Check pre-charge pressure of dia-
phragm expansion vessel.
Check whether BDF valves are
open.
Check system pressure sensor
with external pressure gauge.
89 No central heating and no
DHW heating
Internal circulation pump
blocked
Check circulation pump. Replace if
necessary.
95 Burner not operational OpenTherm remote con-
trol not connected
■
Check connection to the Open-
Therm remote control.
■
If OpenTherm is not required, set
C.7 in the commissioning assis-
tant to a value not equal to 14.
104 Depending on configuration
of EM-EA1 extension (DIO
electronics module)
External fault message in-
put active
Check connected external appli-
ance.
142 Burner in a fault state Communication restriction
on CAN bus. INR
Check the fan unit for correct func-
tion. For this, check the stepper
motor of the fan unit (reference run
with mains ON).
If the fault still persists, check the
plug-in connections and cables of
the CAN bus.
Check further CAN bus subscrib-
ers. If fault occurs repeatedly, re-
place fan unit.
161 Burner in a fault state HBMU heat management
unit data memory access
fault
Reset the appliance.
If the fault occurs repeatedly, re-
place the HBMU heat management
unit. See chapter "Replacing the
HBMU heat management unit".
163 Burner in a fault state Checksum error, data
memory access, HBMU
heat management unit
Reset the appliance.
If the fault occurs repeatedly, re-
place the HBMU heat management
unit. See chapter "Replacing the
HBMU heat management unit".
182 No DHW heating Short circuit, outlet tem-
perature sensor (if instal-
led)
Check outlet temperature sensor
(plug X7, cores 3 and 4). Measure
sensor input on HBMU heat man-
agement unit. Set value: 3.3 V
–
with sensor disconnected
183 No DHW heating Lead break, outlet temper-
ature sensor (if installed)
Check outlet temperature sensor
(plug X7, cores 3 and 4).
Troubleshooting
Fault messages (cont.)
6179762
Diagnosis