Bosch 14/19CBI - Manual (Page 38)

FAIL POINT E 'BURNER LOCK
OUT'
Is the gas supply
connected and at the
correct pressure?
Remove boiler casing.
Reset and restart
the boiler.
Can a flame be seen
through the spyglass?
Note: there is a 20
second delay from fan
on to spark.
Yes
No
Rectify gas supply
problem.
No
TURN OFF GAS SUPPLY.
Remove inner casing
cover.
Reset and restart boiler.
Does a spark occur
across the electrodes?
No Are the electrodes
and gap and
connections
in good order?
No
Repair or replace
spark electrode
or HT leads.
Yes
Replace control board.
Yes
During spark period
is there 216V D.C.
across the pins at
connector X2?
Replace gas valve or
check cable to it.
Yes
No
Yes
TURN OFF GAS SUPPLY.
Remove the combustion
chamber cover. Is the
sense (right) electrode
and lead in good
condition and is gap
correct?
See Section 15.4.3
No
Repair or replace
flame sense
or cable to it.
Replace control board.
Note: It is not possible
to reliably check the
cross light performance
of the burner.
In the unlikely event of
such a fault, investigate
condition of flue,
burner and injector.
Also check polarity of
mains voltage supply.
Yes
38
NOTE: Do not attempt to light the boiler
with the combustion chamber cover
removed.