38
Mexico Super 100 FF & 125 FF -
Installation
FAULT FINDING
Check all connections to PCB.
If no fault found, replace PCB
Reset the overheat 'stat. Set control
'stat to maximum. Allow the boiler to
reach temperature - if the overheat
'stat trips again, measure flow
temperature.
If above 90°C replace control 'stat.
If below 90°C replace overheat 'stat.
START
Check that the mains on neon
'
I
3' is illuminated.
YES
NO
YES
YES
NO
Is there a live supply to both
terminals of overheat 'stat?
(if fitted)
Is the ignition electrode sparking?
YES
YES
YES
Change fan
YES
NO
Rectify bad connection
Check mains supply and fuses.
Check programmer and system
thermostats are all ON. Check that
boiler connections are OK .
Check that the boiler thermostat
is set at maximum and the mains
on/off switch is ON.
Is the fan turning ?
Check connections to pressure
switch. If no faults found, change
pressure switch.
Replace the boiler thermostat
Check connections and leads to
pressure switch/boiler thermostat
and check that fan is operating.
Check all connections to PCB.
If no fault found change PCB.
YES
Check pressure switch sensing
pipes for blockages, bad
connections and reversed
connection.
Is pressure difference at switch
greater than 0.9 mbar?
Change fan
YES
NO
Change
pressure switch
Does the pilot light ?
NO
YES
NO
YES
Does the
spark stop
after pilot is
lit?
NO
Is there a gas supply
to the boiler?
Is the pilot injector
blocked?
YES
Replace
gas valve
NO
Is there a supply on
terminals of main gas
valve?
YES
NO
YES
NO
NO
Is there a supply on the fan
connector at PCB ('Molex '
marked 'FAN'?).
YES
YES
NO
NO
Check the polarity of
the mains supply.
Check the continuity of
the ignition lead from
connector to electrode.
Does the spark now
cease when gas is lit ?
Ensure pilot and
main gas valve
leads are not
crossed over.
Is there a supply
voltage at pilot
gas valve?
Is there a live
supply on the
red lead to
pressure
switch?
NO
Is there a regular
spark from tube 'SG1'
on the PCB?
Can the overheat 'stat
be reset when the
system is cold ?
NO
YES
NO
Replace fuse BUT, before
attempting to start boiler, check
for short between live and
neutral, also between live and
earth, on all items plugged into
PCB
Check all connections to PCB.
If no error found, replace PCB.
Is there continuity
across the control
thermostat ?
YES
NO
NO
YES
Has the fuse blown on PCB ?
NO
NO
Is there a live supply on the
violet lead to pressure switch?
Is there a
supply at
the fan ?
Replace the overheat thermostat
Does main burner
cross-light from pilot?
Is the main burner
injector clear?
Replace main gas
solenoid valve
Check gap at ignition electrode.
Check electrode and lead are
undamaged, and not close to
earthed metalwork.
F
AUL
T FINDING
