Ideal Boilers i 30 - THERMISTOR FAULT DIAGNOSIS

53
Fault Finding
Fault Finding Fault Finding Fault Finding Fault Finding Fault Finding
i combi - Installation and Servicing
75 ALTERNATING ‘F’ AND ‘4’ - FLOW THERMISTOR FAULT
Check the 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
Is the Thermistor value correct?
Is there continuity between the PCB and
the Thermistor?
Fit a new Thermistor
NO
Check and replace
wiring as necessary
76 ALTERNATING ‘F’ AND ‘5’ - RETURN THERMISTOR FAULT
YES
NO YES
Replace PCB
Check the 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
Is the Thermistor value correct?
Is there continuity between the PCB and
the Thermistor?
Fit a new Thermistor
NO
Check and replace
wiring as necessary
YES
NO YES
Replace PCB