Viessmann VITOCAL 300-G Installation And Service Instructions Manual page 140

Troubleshooting
Messages
(cont.)
Message
System characteristics Cause
B2 KM BUS EEV
B4 A-D converter
B5 EEPROM
B9 KM BUS solar
140
Communication fault
with EEV controller
(refrigerant circuit con-
trol), heat pump stage 2
(type BWS)
Internal fault ADC (ana-
logue digital converter,
reference), ribbon cable
between sensor PCB
and main PCB faulty, or
PCBs faulty
Internal fault, EEPROM
Communication error -
KM BUS solar control
unit, or sensor S3 of
Vitosolic faulty
Measures
Check KM BUS connec-
tion. At the connection
between KM BUS and
EEV, a fluctuating DC
voltage between approx.
20 V and 30 V can be
measured at the controller
and sensor PCB at termi-
nals X5.14 and X5.15
(connections are parallel
to plug aVG).
Check leads/cables;
check power supply to
EEV controller PCB;
replace PCB if required.
Check PCB; if required,
replace in the following
order: Controller and sen-
sor PCB, main PCB, pro-
gramming unit.
Replace coding card.
■ Check parameter
"Solar control unit
type 7A00".
■ Check connection to
Vitosolic.
■ Check Vitosolic sensors
and replace if required
(see Vitosolic installa-
tion and service instruc-
tions).