Set Appliance State:

Set Multimeter to Resistance Set meter to measure resistance
Isolate Mains Power to appliance as per TOPs P4
Remove connector plug 5 (connections 32-39)

Measurement:

Measurements should be made on the disconnected end of the plug and not the PCB.
HW Tap ON:
Measure resistance between connection 39 on connector plug and DHW Thermostat (connection 2). Resistance should be short circuit.
HW Tap OFF:
Measure resistance between connection 39 on connector plug and DHW Thermostat (connection 2). Resistance should be open circuit.