41
SECTION 4 - FAULT FINDING
4.12 ‘F4 OR L4’ - FLOW THERMISTOR FAULT
Disconnect the wiring from the Flow Thermistor
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?
YES
Is the wiring securely connected to the low voltage 6 way
connector at the front left hand side of the PCB?
YES
Replace PCB
Fit a new Thermistor
NO
Securely connect the wiring to the PCB
Is the wiring securely connected to the Flow Thermistor
(located in the top of the Heat Exchanger?)
YES
NO
Securely connect the wiring to the Flow
Thermistor
NO
4.13 ‘F5 OR L5’ - 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 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?
YES
Is there continuity between the PCB and the Thermistor?
YES
Replace PCB
Fit a new Thermistor
NO
Check and replace wiring as necessary
NO
