Set Appliance State:
Set Multimeter to Resistance 
Isolate Mains Power to appliance as per TOPs P4
Measurement:
Turn Boiler Control Thermostat fully anticlockwise.
Measure open circuit between the Red + Blue wires and open circuit between Black + Blue wires.
Turn Boiler Control Thermostat fully clockwise.
Measure short circuit between the Red + Blue wires and short circuit between Black + Blue wires.
Measure open circuit between the Red + Blue wires and open circuit between Black + Blue wires.
Turn Boiler Control Thermostat fully clockwise.
Measure short circuit between the Red + Blue wires and short circuit between Black + Blue wires.
