Set Appliance State:
Mains Power Off
Mode selector switch to Off/Reset position
Set Multimeter to AC Volts 
Central heating temperature control set to maximum
| WARNING! - Mains voltage is expected during test follow TOPs P4 live testing procedure |
Measurement:
Mode selector switch to CH position.
Measure the voltage across the connection 1 on connector M16 on the main PCB and a suitable neutral.
Notes:
Connections are numbered top to bottom.
Ensure there is a link fitted between white and white/red wire on the integral clock connector block.
Measure the voltage across the connection 1 on connector M16 on the main PCB and a suitable neutral.
Notes:
Connections are numbered top to bottom.
Ensure there is a link fitted between white and white/red wire on the integral clock connector block.
Isolate as per TOPs P4
and refit as necessary