Set Appliance State:
Gas Off
| Isolate Mains Power to appliance as per TOPs P4 |
Set Multimeter to Resistance 
Ensure that the Boiler is not in an overheat condition
Measurement:
Disconnect the Brown wire and the Blue wire from the CH Limit Thermostat and measure the Resistance across the Thermostat.
Reconnect wires after test.
Reconnect wires after test.
Isolate as per TOPs P4
and refit as necessary