Set Appliance State:

Isolate Mains Power to appliance as per TOPs P4
Set Multimeter to DC Volts Set meter to measure DC Volts
Gain access to PCB (use Insulation Mat as required)
WARNING! - Mains voltage is expected during test follow
TOPs P4 live testing procedure
Mains Power On

Measurement:

Reset appliance if required.
(press and hold the power button for 4 seconds then release)
Test 1:
Measure the DC voltage between pin 14 on connector X2 and an earth (use the copper pipe to the gas valve as earth) before the pump begins to run for the self check and make a note of the reading (a system pressure of 1.2 bar will give an initial voltage of approximately 1.8 Vdc)
Test 2:
Monitor the voltage when the pump runs, there should be an increase of approximately 0.3 Vdc from the original reading measured when the pump runs.
Is there an increase in voltage when the pump is running as described above?