Set Appliance State:

Set Multimeter to Resistance Set meter to measure resistance
Ensure the Boiler has been operating in its
low mode and that it has reached its low operating temperature
WARNING! Mains voltage is expected during test, follow TOPs P4 live testing procedure
Mains Power On

Measurement:

Isolate Mains Power to appliance as per TOP's P4

Disconnect the White spaded wire and the Yellow spaded wire from the low Thermostat (1)
Measure the resistance across the Thermostat.