Set Appliance State:

Isolate Mains Power to appliance as per TOPs P4
Set Multimeter to Resistance Set meter to measure resistance
There are two thermistor sensors on the appliance they are located at the r/h side of the heat exchanger in the flow and return header, due to the position it will be easier to check the resistance of the thermistor at the plug connections on the PCB.
Note: The resistance will depend on the temperature of the appliance.
The higher the temperature the lower the resistance.

Measurement:

Test 1: Remove connector X11 from the PCB.
Check resistance across the red leads at the disconnected connector.
The resistance should conform to the table below:
Test 2: Remove connector X8 from the PCB.
Check resistance across green leads at the disconnected connector.
The resistance should conform to the table below:
Temperature °CResistance in kOhms
20 - 308 to 16
30 - 40 6 to 10
40 - 503.9 to 8
50 - 602.5 to 5.5
60 - 701.5 to 3.0