Set Appliance State:
Mains Power Off
Set Multimeter to DC Volts 
DHW tap on
| WARNING! Mains voltage is expected during test, follow TOPs P4 live testing procedure |
Measurement:
Measure voltage across connection 5 (red lead) and connection 6 (red lead) on connector marked X6.
Expected voltage approximately 36 volts DC.
Turn function selector switch to DHW.
Measure voltage across the same connections connection 5 (red lead) and connection 6 (red lead) on connector marked X6.
Voltage should drop to zero as the microswitch makes.
Expected voltage approximately 36 volts DC.
Turn function selector switch to DHW.
Measure voltage across the same connections connection 5 (red lead) and connection 6 (red lead) on connector marked X6.
Voltage should drop to zero as the microswitch makes.
Isolate as per TOPs P4
and refit as necessary