ac wires dohc vs sohc?

[alpha180sx]

car is a 1990 sohc auto 240sx hatchback

my issue is this.

my ac fan dont turn on when i press my ac switch.

what i tested so far

fuse is is good with voltage on it,i tested it with vom
tested my relay also and works
ac fan tested as well and it works when i run a fresh direct line from the battery.

im trying to trace the line but im not familiar with sohc wiring unless they are the same as the dohc.

i can easily wire it up with new wire with new relay but i want to use and retain my factory setting to turn the ac fan.

if anyone can helps pls do. i appreciate it.