Set Appliance State:
| Isolate Mains Power to appliance as per TOPs P4 |
Set Multimeter to DC Volts 
CH Demand
Gain access to PCB
Use insulation mat as required
Ensure boiler is cool
Use insulation mat as required
Ensure boiler is cool
| WARNING! - Mains voltage is expected during test follow TOPs P4 live testing procedure |
Measurement:
With the fan running measure the DC voltage between the lower white wire (pin 6) at connector J4 on the PCB and a suitable earth point.
Expect approx. 6.5V DC.
Expect approx. 6.5V DC.
Isolate as per TOPs P4
and refit as necessary