Set Appliance State:
Set Multimeter to Resistance 
Ensure the Boiler has been operating in its
low mode and that it has reached its low operation cut off temperature (approx 68 deg C)
low mode and that it has reached its low operation cut off temperature (approx 68 deg C)
| WARNING! Mains voltage is expected during test, follow TOPs P4 live testing procedure |
Measurement:
| Isolate Mains Power to appliance as per TOP's P4 |
Disconnect the White spaded wire and the Yellow spaded wire from the Lo Thermostat and measure the resistance across the Thermostat terminals.
Note:
It may be necessary to reduce heating load by turning off some radiators to reduce time taken for this test.
Isolate as per TOPs P4
and refit as necessary