Set Appliance State:
| Isolate Mains Power to appliance as per TOPs P4 |
Set Multimeter to AC Volts 
Turn Hot Water Tap On
Gain access to PCB use insulation mat as necessary
Loosen connector for fan slightly to expose test pins
Loosen connector for fan slightly to expose test pins
| WARNING! - Mains voltage is expected during test follow TOPs P4 live testing procedure |
Measurement:
Using the test pins check for mains voltage between the black and red wires on ST1.
Note:
Boiler sends mains voltage between black and red for
DHW and black and white for CH.
Note:
Boiler sends mains voltage between black and red for
DHW and black and white for CH.
Isolate as per TOPs P4
and refit as necessary