I don't have the 620 wiring schematic[s] but here is your typical Nissan 5 terminal Ignition Switch: -
Attachment:
Nissan 5 wire ignition switch wiring.jpg [ 28.44 KiB | Viewed 890 times ]
B is 12v or
Battery supply
IG is the 12V supply to the
IGnition circuit
R is the 12V supply to the ignition bypass
Resistor
A is the 12V supply to the
ACCessories
S is the 12V supply to the starter motor
Solenoid
You will need to use a multi meter and rotate the switch to each position to verify what each wire colour does.