Viessmann MPA51 Operating And Service Instructions page 21

Diagnosis
(cont.)
Fault Display
code *1
F 54 F 54
F 55 F 55
All fault codes are saved to the fault memory and the last 10 can be called up.
*1
System charac-
teristics
PWM values in-
correct
Parameter memo-
ry stick fault
Cause
EEPROM of
memory stick
modified or de-
leted. Memory
stick faulty
Memory stick faul-
ty
Diagnosis
Measures
Replace memory
stick.
I Danger
Plug-in termi-
nals on the
burner control
unit are 'live'.
Only replace
memory stick
when burner
control unit
has been iso-
lated from
power supply.
Replace memory
stick.
I Danger
Plug-in termi-
nals on the
burner control
unit are 'live'.
Only replace
memory stick
when burner
control unit
has been iso-
lated from
power supply.
21