Viessmann VITODENS 333 Service Instructions Manual page 11

Further details regarding the individual steps
Yes
Fan starts
Yes
Differential pres-
sure sensor
enables start
(0.75 V across
terminals X8.5
and X8.6)
Yes
Ignition
Yes
Gas combination
valve opens
Yes
Ionisation cur-
rent builds
(higher than
5 µA)
Symbol A
Initial start-up, inspection, maintenance
After approx.
51 seconds
No
Fault
F9
After approx.
51 seconds
No
Fault
E6
Fault
No
F4
Fault
No
F4
Fault
No
F4
(cont.)
Check cables and
plug-in connec-
tions
Check fan cables
and fan plug-in
connections,
check fan
Check the ignition
module (control
voltage 230 V
across plugs X2.1
and X2.2)
Check the gas
combination valve
(control voltage
230 V), check the
gas supply pres-
sure
Check electrode
adjustment and
check the gas
pipe for airlocks
11