Fault Finding - Baxi Bermuda Inset 2 Boiler 50/4 E Manual

START
Ensure all external controls
are calling for heat. Turn the
thermostat potentiometer
off, wait 10 seconds and
turn to HIGH.
Is
YES
the permanent
live neon lit ?
NO
Is
YES
there mains
voltage between terminals
'L' & 'N' ?
NO
Check mains
fuse at spur
Check polarity of wires
in plug connector
Check fuse on
P.C.B. (4 AMP)
Replace P.C.B.
POTENTIOMETER PLUG
Red/Blue
Orange/Black
Yellow/Red
26
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Is
YES
the SW live
neon lit, indicating switched
live ?
NO
Is
there mains
voltage between terminals
'SL' & 'N' ?
NO
YES
Check external
controls/wiring
Check polarity of
wires in plug
connector
Replace P.C.B.
Connect Test
Leads Here

10.0 Fault Finding

Before starting FAULT FINDING carry out
preliminary electrical system checks i.e. Earth
Continuity, Polarity, Short Circuit and Resistance
to Earth.
Is
YES
the ignition
neon lit, indicating start of
ignition sequence ?
NO
Check boiler
thermostat is calling for
heat (turn fully
clockwise)
Disconnect and check
resistance across sensor
(1M ohm @ 25 o C)
remove from boiler if hot
NO
Check potentiometer
resistances are correct
(see below)
YES
Replace P.C.B.
POTENTIOMETER RESISTANCE CHECKS
Set multimeter to 2M OHM scale. Turn potentiometer off. Connect
multimeter leads at the top of the plug across red/blue wire and
orange/black wire. Reading should be open circuit. Switch potentiometer
on, reading should be between 0.7 & 1.3M OHMs. Slowly turn
potentiometer to full on; reading should decrease, proportionate to knob
position, down to between 0.24 & 0M OHMs.
Connect multimeter leads to orange/black and yellow/red wires. Reading
should be between 0.7 & 1.3M OHMs. Slowly turn potentiometer down,
reading should decrease, proportionate to knob position, down between
0.2 & 0M OHMs.
Turn potentiometer completely off, reading should be open circuit.
Is
there a clear
& constant spark
between the ignition
electrode & pilot
burner ?
NO
Check electrode & lead
for breaks in the
insulation
Check connections
Check spark gap
(2.5 - 4.0mm)
Replace P.C.B.
Replace sensor
Replace
potentiometer
YES