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FAULT FINDING
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T FINDING F
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T FINDING
Mexico Super CF445-475 -
Installation & Servicing
Detailed instructions on the cleaning and adjustment or
replacement of faulty components are contained in the
'Servicing' section of this publication.
Before attempting any electrical fault finding ALWAYS carry
out preliminary electrical system checks, i.e. earth continuity,
polarity and resistance to earth using a suitable meter.
Check mains neon on PCB.
Is it illuminated?
YES
NO
Is there a live supply to
both terminals of overheat
'stat? (If no overheat 'stat
fitted go to next step).
YES
NO
Check the control 'stat is
set to max and mains
switch is on.
Is there a regular spark
from tube SG1 on the
PCB?
Check mains supply and fuses. Check controls are calling for heat. Check
boiler wiring connections are OK. Check if the TTB downdraught thermostat has
operated in adverse wind conditions.
NO
Can the overheat thermostat
be reset with the system cold?
Replace fuse but before restoring power check for short circuit
between L/N and L/Earth on all components plugged into the PCB.
Check gap at ignition electrode. Check electrode and leads are not damaged.
Check the lead is not shorting to earth. Rectify as necessary.
Replace the overheat 'stat.
Has the fuse on the PCB blown?
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.
YES
Is there a spark at the
ignition electrode?
Does the pilot burner light?
NO
Is there a gas supply to the boiler &
has the gas supply been purged of air?
Connect or rectify and
purge the system of air.
NO
YES
Replace the PCB.
NO
YES
NO
YES
NO
YES
NO
YES
NO
Ensure pilot and main gas valve leads are not crossed
over. Is there a supply voltage at the pilot gas valve?
Is the pilot injector
blocked or the pilot
supply pipe damaged?
Rectify or replace as necessary
Check connections at the gas
valve and rectify as necessary.
If no connection fault found
replace PCB.
Replace gas valve
YES
Does the spark stop
after the pilot is lit?
YES
Does the main burner
cross-light from the pilot?
NO
Check polarity of mains supply. Check
continuity of ignition lead.
Does spark now stop when pilot is lit?
Is there a supply voltage at the main gas valve?
Check connections
to PCB.
If no fault change
PCB.
Is the main injector blocked?
Replace main gas solenoid valve.
Does the main burner light?
YES
NO
YES
Clear blockage and refit.
Does main burner light?
YES
NO
Replace
gas
valve
YES
NO
YES
NO
Boiler
operating
satisfactorily
Check for correct gas
supply pressure.
Rectify as necessary.
NO
YES
YES
NO
YES
NO
200943-1.p65
3/4/2004, 1:58 PM
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