Set Appliance State:
Mains Power Off
Set Multimeter to DC Volts 
| WARNING! - Mains voltage is expected during test follow TOPs P4 live testing procedure |
Measurement:
Reset appliance if required (Press reset button once then release)
Measure the DC voltages between each of the test points at connector X51 on the back of the display PCB as listed below to the earth point on the boiler chassis.
The Voltages should conform approximately to the table below:
Measure the DC voltages between each of the test points at connector X51 on the back of the display PCB as listed below to the earth point on the boiler chassis.
The Voltages should conform approximately to the table below:
| Test point | DC Volts | GND | 0 |
| RES_SW | 4.7 |
| EBUS | 21.8 |
| 5V | 5 |
| 24V | 24 |
| PEBUS | 5 |
 dcp connector x51.gif)
Isolate as per TOPs P4
and refit as necessary