Set Appliance State:
Set Multimeter to DC Volts 
CH Demand
Isolate Mains Power to appliance as per TOPs P4
Selector Switch Summer position
Link pins 1 and 2 of five pole connector on mounting frame
Selector Switch Summer position
Link pins 1 and 2 of five pole connector on mounting frame
| WARNING! Mains voltage is expected during test, follow TOPs P4 live testing procedure |
Measurement:
Measure DC voltage across connector CN4 connections 3 (Blue) and 4 (Grey). The negative probe goes on connection 3 and the positive on connection 4. Voltage should be less than 0.5 Volts DC.
Remove link.
Remove link.
Isolate as per TOPs P4
and refit as necessary