Set Appliance State:
| Isolate Mains Power to appliance as per TOPs P4 |
Set Multimeter to DC Volts 
Gain access to PCB (use Insulation Mat as required)
Boiler On
SUMMER/WINTER switch set to WINTER
System calling for heat
Boiler On
SUMMER/WINTER switch set to WINTER
System calling for heat
| WARNING! - Mains voltage is expected during test follow TOPs P4 live testing procedure |
Measurement:
Measure the DC voltage between D17 (Black wire) and D16 (Black wire) on distribution board.
Voltage should be between 3 - 8V DC dependent on the Central Heating flow temperature.
Voltage should be between 3 - 8V DC dependent on the Central Heating flow temperature.
Isolate as per TOPs P4
and refit as necessary