IT should come on with the A/C
Check fuse # 25 and 27 make sure they are good.
Then you pul the plug out of the right side of the radiator and you have 3 pins in it.
shot the brown wire with one wire (don't remember color) and you should have low speed
Do with again with the other wire and you should have high speed.
If none are working... check if the fan isn't seized up. Older fan tend to seize up.
'85 Euro 635csi Race Turbo, megasquirt, Group A
'92 525i Touring 5 speed, 3.46 diff, UUC 8.5lb flywheel, soon to be turbo.
'02 Subaru WRX Wagon with STI springs, bigger sway bars