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)
No demand
WARNING! - Mains voltage is expected during test follow
TOPs P4 live testing procedure
Mains Power On

Measurement:

Allow self-check to complete.
Test 1. Measure the DC voltage across pins 1 to 6 of connector X3 to a suitable earth connection.
Expected voltage approx. 24 V DC on all pins, if voltages for Test 1. are not as expected then choose that option below.
Test 2. Power off the boiler (see note), wait 10 seconds then reinstate the power, during the initial 10 seconds of self-test, measure the DC voltage across pin 1 of connector X3 to a suitable earth connection.
Voltage should fluctuate during the initial 10 seconds then return to 24V DC (Repeat as required until test complete).
Test 3. Repeat test 2 for pins 3,4 & 6.
Note. Power off boiler using the On/Off switch located under the boiler facia, right hand-side.