49
Does fan run?
Does yellow fan operation
indicator ( ) flash?
Does yellow flame
indicator ( ) flash?
Does yellow fan operation
indicator flash or glow?
Check air/flue gas system is
correctly fitted and not
obstructed. Check pitot tube
(in fan outlet) and air hoses
are not obstructed and are
correctly aligned. Check or
replace air pressure switch.
Check fan/flue gas system
Sheet E
Is 230 V present across
fan ter
minals?
Does yellow central heating
demand indicator ( )
glow?
No heat demand.
Go to sheet C.
Check/replace fan.
Ye
s
No
Ye
s
Ye
s
No
No
No
No
Ye
s
Switch main on/off control off
and on again.
Ye
s
Check NTC. Disconnect NTC lead at plug (3, fig. 37).
Does fan run now?
Check connection to NTC
temperature sensor
, clean and
tighten. Check NTC not
shor
tened to ear
th. If O.K
replace NTC sensor
.
Replace electronic boards.
No
Ye
s
Does yellow flame
indicator ( ) glow?
Defective electronic
boards.
No
Does bur
ner light?
Ye
s
Go to sheet F
.
No
Go to sheet H.
Ye
s
Ye
s
Does yellow flame
indicator ( ) flash?
No
Check pitot tube (in fan outlet)
and air hoses are not
obstructed and correctly
aligned. Check or replace air
pressure switch.
Ye
s
Does fan run now?
No
Ye
s
No