Set Appliance State:

Isolate Mains Power to appliance as per TOPs P4
Set Multimeter to DC Volts Set meter to measure DC Volts
CH Demand
WARNING! - Mains voltage is expected during test follow
TOPs P4 live testing procedure
Mains Power On

Measurement:

Allow ignition sequence to commence.
Test for DC voltage between connection 4 (brown wire)
on H5 at the PCB and a suitable earth.
Observe voltage as ignition sequence progresses.
At rest expect reading of Approx. 77 VDC, during ignition attempts Voltage will increase to Approx. 170 VDC.
When flame is present expect voltage to drop to Approx. 10-20 VDC.
Note:
Ensure that spark generator is correctly mounted and secured to the heat exchanger bracket. If incorrectly fitted it has been found to affect rectification.