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70 ALTERNATING 'F' AND '4' - CONTROL / NO FLOW THERMISTOR FAULT
Remove the Control/No Flow Thermistor from the
Heat Exchanger and disconnect the wires.
Check the resistance using a suitable multimeter
connected across the thermistors terminal pins.
At 25
C
expect
o
At 60
C
expect
o
At 85
C
expect
o
Is the Thermistor value correct?
71 ALTERNATING 'F' AND '5' - RETURN THERMISTOR FAULT
Remove the Return Thermistor from the CH Return
Pipe and disconnect the wires.
Check the resistance using a suitable multimeter
connected across the thermistors terminal pins.
At 25
C
expect
o
At 60
C
expect
o
At 85
C
expect
o
Is the Thermistor value correct?
72 ALTERNATING 'F' AND '6' - OUTSIDE SENSOR FAULT
Is the wiring securely connected at both the boiler and
Outside Sensor?
Disconnect the wires to the outside sensor.
Check the resistance using a suitable multimeter
connected across the Outside Sensors terminal pins.
At 0
C
expect
o
At 15
C
expect
o
At 30
C
expect
o
Is the Outside Sensor value correct?
73 ALTERNATING 'c' AND '2' - BCC FAULT (BOILER CHIP CARD)
Is the correct BCC for the boiler securely inserted into the
slot at the front left of the PCB?
(identified by the label on the BCC)
Replace the BCC with a new BCC (that is correct for the
boiler). After switching power on and 'c0' being shown,
press restart. Is 'c2' still shown?
RESTART PROCEDURE - To restart boiler, turn mode knob to restart position and immediately turn knob back to required setting.
Installation and Servicing
FAULT FINDING
9,700 - 10,300
Ohms
2,400 - 2,600
Ohms
1,000 - 1,100
Ohms
9,700 - 10,300
Ohms
2,400 - 2,600
Ohms
1,000 - 1,100
Ohms
YES
31,000 - 35,000
Ohms
15,000 - 16,500
Ohms
7,700 - 8,500
Ohms
YES
NO
Fit a new Thermistor
YES
Is there continuity between the PCB and Thermistor?
YES
Replace PCB
NO
Fit a new Thermistor
YES
Is there continuity between the PCB and Thermistor?
YES
Replace PCB
NO
Securely connect the wiring at both the
boiler and Outside Sensor
Fit a new Outside Sensor
NO
Is the wiring securely connected between the
YES
incoming terminal block boiler connection of
the Outside Sensor and the PCB?
YES
Replace PCB
NO
Securely insert the correct BCC for the boiler
into the PCB and after switching power on and
'c0' being shown, restart boiler.
Note. Ensure the correct orientation of BCC by
placing "TOP" side up.
YES
Replace PCB
NO
Check and replace wiring as
necessary
NO
Check and replace wiring as
necessary
NO
Securely connect the wiring at
the Terminal Block and the PCB
53
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