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12.0 Fault Finding
37
© Baxi Heating UK Ltd 2009
Check and correct if necessary
1. The mechanical set of the gas valve
(CO2 values - see instruction)
2. Flame sensing electrode and lead connections
3. Flame sensing electrode position
Flame current should be more than 0.5 μA
Replace PCB
YES
Replace flame sensing electrode
NO
Check the gas supply pressure:
For Natural Gas greater than
10 - 11 mbar
I
Replace Safety Thermostat
YES
Overheat Thermostat or
Condensate Safety Float Switch
operated or faulty
Allow to cool. Continuity
across thermostat terminals
more than 1.5 ohm
2.
1.
H
K
J
L
Press the Service Reset switch
for 5 seconds
Fan connections correct at fan.
PCB - X401 connector terminals 5,6,7 & 8
YES
Replace fan
Temperature sensors faulty.
Cold resistance approximately
10kΩ @ 25° C (CH sensor)
(resistance reduces with increase in temp.)
NO
Replace sensor
YES
If pump is running the heat exchanger could be
obstructed
Replace heat exchanger
1.
2.
Restore Boiler Control defaults
NO
Continuity across plug
terminals at 3 & 4 of connector
X401 more than1.5 ohm
Replace PCB
NO
YES
Condensate drain system fault
Check condensate system
and Pump
Replace Safety Float Switch
or wiring
NO
IMPORTANT:There is no limit to the number of repeated ‘Service Reset’
operations but the Boiler Control must be refreshed by ‘Restoring Boiler
Control Default’ as described on p.34 following the final ‘Service Reset’ and
before the Boiler Control reset is re-used.
YES