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FAULT FINDING
F
AUL
T FINDING F
AUL
T FINDING F
AUL
T FINDING F
AUL
T FINDING F
AUL
T FINDING
isar + programmer -
Installation and Servicing
Does the pump setting give a differential across
the boiler in excess of 25
o
C ?
Can the overheat condition be reset by pressing the
boiler select (reset) button when the system is cold ?
Replace the system pump
Set CH control knob to maximum.
If the overheat trips again measure the flow temp:
Over 90
o
C
Check control thermistor
(
Refer to Frame 84)
Under 90
o
C
Replace overheat 'stat
YES
YES
Check that the pump is rotating freely.
Is differential now below 25
o
C ?
NO
NO
82 L.....A..... (OVERHEAT ERROR)
Fill and vent the system and open all
isolation valves
YES
Is the boiler and CH system filled with
water and all isolation valves open ?
OK
NO
YES
NO
Replace overheat thermostat
83 L....8.....
(FAN ERROR)
Is nominal 330 V DC present across
red and blue at the fan connector as
boiler select (reset) button is pressed?
Replace fan
YES
NO
Replace harness
84 H.....1..... (CONTROL THERMISTOR [FLOW] ERROR)
YES
Is there continuity between the
PCB and the thermistor ?
Check resistance using a suitable multimeter
connected across the thermistor’s terminal pins
At 25
o
C expect
9,700 - 10,300
Ohms
At 60
o
C expect
2,400 - 2,600
Ohms
At 85
o
C expect
1,000 - 1,100
Ohms
Remove the boiler control thermistor from the
CH flow pipe and disconnect thermistor wires.
Are the thermistor values correct ?
Replace the thermistor
NO
NO
YES
Replace PCB
Check and replace wiring as necessary
Replace PCB
YES
Is 14V DC present across
yellow and pink at the fan
connector?
Check wiring harness for continuity.
Is there continuity?
NO
YES
NO
202851-1new.pmd
17/11/2006, 07:41
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