Set Appliance State:
| Isolate Mains Power to appliance as per TOPs P4 |
Set Multimeter to Resistance 
CH Demand
Gain access to PCB (use Insulation Mat as required)
| WARNING! - Mains voltage is expected during test follow TOPs P4 live testing procedure |
Observation:
Locate the X20 connector on the PCB and test the voltage to earth on the White wire (Pin 3).
Monitor the voltage on this wire for at least 1 min after placing a demand, you should see the voltage change as the fans Hall Sensor sends the signal back to the PCB during each ignition attempt.
The table below shown the approximate voltages during normal operation:
Monitor the voltage on this wire for at least 1 min after placing a demand, you should see the voltage change as the fans Hall Sensor sends the signal back to the PCB during each ignition attempt.
The table below shown the approximate voltages during normal operation:
| Voltage | |
| Fan Stopped | 0v |
| Fan Running | 5v |
Isolate as per TOPs P4
and refit as necessary