Set Appliance State:
| Isolate Mains Power to appliance as per TOPs P4 |
Set Multimeter to Resistance 
Ensure the Boiler has been operating and has reached its full operating temperature. It may be necessary to reduce the heating load by turning off some radiators to reduce time for boiler to reach temperature.
Measurement:
Disconnect connection 9 (Brown wire) and connection 7 (Purple wire) from the Control Thermostat and measure the resistance across connections 9 and 7 on the Thermostat.
Isolate as per TOPs P4
and refit as necessary