Viessmann Vitodens 100-W WB1B Installation And Service Instructions Manual page 35

Fault messages on the display
Fault code System character-
on the dis- istics
play
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
Fd Burner blocked
(cont.)
Cause Measures
No flame signal is Check the ionisation
present electrode and leads,
measure the ionisation
current, check the gas
pressure, check the gas
train, ignition, ignition
module and condensate
drain.
Press "Reset" (see
page 36).
The fuel valve Check the gas train.
closes too late Check both control
paths.
Press "Reset" (see
page 36).
Fan speed too Check the fan, check
low during the the fan cables and sup-
burner start ply; check the fan con-
trol.
Press "Reset" (see
page 36).
Fan not at stand- Check the fan, fan con-
still necting cables and fan
control.
Press "Reset" (see
page 36).
Control unit or Replace boiler coding
boiler coding card card or control unit
faulty
Burner control Check ignition electro-
unit fault des and connecting
cables. Check whether a
strong interference
(EMC) field exists near
the equipment.
Press "Reset" (see
page 36).
Replace control unit if
the fault persists.
Troubleshooting
35