Fault finding and diagnosis | 61AU/NZ
6 720 646 195a (2010/11)
7 Fault finding and diagnosis
7.1 Fault finding
The electronic control system for this boiler
incorporates a blue central indicator. This normally
confirms the permanent mains supply but, by flashing at
different rates during a fault, provides a guide to the
cause as listed.
This fault finding system assumes that the boiler has
been operating normally until the time of failure (i.e. not
a first installation error).
Preliminary electrical system checks are the first
electrical checks to be carried out during a fault-finding
procedure. On completion of the Service/Fault-Finding
task which has required the breaking and remaking of
electrical connections, check:
(a) Earth continuity,
(b) Short circuit check,
(c) Polarity and
(d) Resistance to earth.
This fault finding information is for guidance
only. Robert Bosch cannot be held
responsible for costs incurred by incorrectly
diagnosed faults.
Blue light
indication
Lockout
reset button
Fault Possible solution/check
Off Off No power at
control board
Permanent mains supply to boiler.
Fuse F1 - 2.5A or Fuse F3 - 0.5A.
Transformer (primary coil below 60 Ω, both secondary coil below
10 Ω).
Otherwise replace control board.
On Off Boiler not
operating
during central
heating demand
Live demand at ST10-L
R
(from external room thermostat/timer)
Fascia mounted timer (if fitted)
CH knob in winter position
Control board
Boiler operating
without live
demand at
ST10-L
R
(from
external room
thermostat
timer)
Some older thermostats (containing capacitors) may give a low
voltage return at ST10-L
R
when the thermostat contacts are
open.
Check that there is no permanent live at ST10-L
R
from another
source.
Boiler not
operating
during any
demand.
Fan
Control board
Tab. 28
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