Viessmann VITODENS 300 WB3A, Service Instructions Manual

Page: 99 / 148

Displayed
fault code Const. Weat-
her-
comp. System
character-
istics Cause Remedy
F4 X X Burner in
fault state No flame signal is
present Check the
ionisation
electrode and
leads, mea-
sure the ioni-
sation cur-
rent, check
the gas pres-
sure, check
the gas com-
bination
valve, igni-
tion, ignition
module, igni-
tion electro-
des and the
condensate
drain.
Press
E
.
F7 X X Burner
blocked Differential pres-
sure sensor faulty Check the dif-
ferential pres-
sure sensor
and lead.
F8 X X Burner in
fault state Fuel valve closes
too late Check gas
combination
valve. Check
both control
paths.
Press
E
.
F9 X X Burner in
fault state Fan speed too low
at burner start Check the
fan, check the
fan cables
and supply,
check the fan
control.
Press
E
.
Checking and acknowledging faults
(cont.)
83
Troubleshooting
56
92
550
GB