99
Fault code dis-
played
System characteristics
Cause
Measures
F2
Burner in a fault state
Temperature limiter has
triggered.
Check heating system fill level.
Check circulation pump. Vent the
system. Check temperature limiter
and connecting cables.
Press reset button
R
.
F3
Burner in a fault state
Flame signal is already
present at burner start.
Check ionisation electrode and
connecting cable.
Press reset button
R
.
F7
Burner blocked
Short circuit or lead break,
water pressure sensor
Check the water pressure sensor
and the connecting cable.
F8
Burner in a fault state
Fuel valve closes too late. Check gas train. Check both con-
trol paths.
Press reset button
R
.
F9
Burner in a fault state
Fan speed too low during
burner start
Check fan, fan connecting cables
and power supply to fan; check fan
control.
Press reset button
R
.
FA
Burner in a fault state
Fan idle state not reached Check fan, fan connecting cables
and fan control.
Press reset button
R
.
FC
Burner in a fault state
Gas train faulty, faulty
modulation valve control
or flue gas path blocked
Check gas train. Check flue sys-
tem.
Press reset button
R
.
Fd
Burner in a fault state and ad-
ditional fault b7 is displayed
Boiler coding card missing Insert the boiler coding card.
Press reset button
R
.
Replace control unit if fault per-
sists.
Fd
Burner in a fault state
Burner control unit fault
Check ignition electrodes and con-
necting cables. Check whether a
strong interference field (EMC) ex-
ists near the appliance.
Press reset button
R
.
Replace control unit if fault per-
sists.
FE
Burner blocked or in a fault
state
Boiler coding card or main
PCB faulty, or incorrect
boiler coding card
Press reset button
R
. If the fault
persists, check the boiler coding
card and replace boiler coding card
or control unit if necessary.
FF
Burner blocked or in a fault
state
Internal fault or reset but-
ton
R
disabled
Restart the appliance. Replace the
control unit if the appliance will not
restart.
Note
If subscriber faults occur,
"Subscriber fault ..."
is dis-
played.
Troubleshooting
Fault codes
(cont.)
5773 238 GB
Diagnosis