Set Appliance State:
| Isolate Mains Power to appliance as per TOPs P4 |
Set Multimeter to AC Volts 
Gain access to PCB (use Insulation Mat as required)
| WARNING! - Mains voltage is expected during test follow TOPs P4 live testing procedure |
Measurement:
Test 1:
Monitor the AC voltage between the red and black wires of X10 on the PCB.
Mains voltage should be present for the first 35 seconds after power is turned on to the boiler but will drop out periodically as appliance attempts to move diverter valve through CH / DHW positions.
Test 2:
Mains power OFF then back ON so appliance restarts self check.
Carry out previous test as above but between
the white and black wires of X10 on the PCB.
Monitor the AC voltage between the red and black wires of X10 on the PCB.
Mains voltage should be present for the first 35 seconds after power is turned on to the boiler but will drop out periodically as appliance attempts to move diverter valve through CH / DHW positions.
Test 2:
Mains power OFF then back ON so appliance restarts self check.
Carry out previous test as above but between
the white and black wires of X10 on the PCB.
Isolate as per TOPs P4
and refit as necessary