Viessmann VITODENS 100-W Installation And Service Instructions Manual page 38

Troubleshooting
Fault messages on the display
Displayed System characteris-
fault code tics
F4 Burner in a fault
state
F8 Burner in a fault
state
F9 Burner in a fault
state
FA Burner in a fault
state
FC Burner blocked
38
(cont.)
Cause
No flame signal de-
tected
Fuel valve closes
too late
Fan speed too low
during burner start
Fan not in idle
state
Electrical fan con-
trol (control unit)
faulty
Measures
Check the ionisation elec-
trode and connecting ca-
bles, check the gas pres-
sure, check the gas train,
ignition, ignition module
and condensate drain.
Initiate "Reset" (see
page 39).
Check gas train. Check
both control paths.
Initiate "Reset" (see
page 39).
Check fan, fan connecting
cables and power supply;
check fan control.
Initiate "Reset" (see
page 39).
Check fan, fan connecting
cables and fan control.
Initiate "Reset" (see
page 39).
Check fan connecting ca-
ble; replace if required, or
replace control unit.