Test for fan control unit

Got a 1998 Grizzly 600. Trying to figure out why my "Oil Temp" light does not come on. From what I can tell, the light should come on while the "Start" button is engaged. Yes, I have checked the bulb. The bulb is getting power, but the ground is not working. The wire is good all the way to the plug that goes into the "Fan Control Unit".

I did not see in my service manual where it tells how to check the FCU. Can anyone tell me? I think I have an idea just be looking at the schematic.

Thanks