Heater fan wiring issue - help

I had a working heater, but the fiberglass was shot.
I was able to get a complete working heater from a FABO member.
I finally switched them today, and the fan does not work.
So, I checked the wiring diagram: 1 black wire from the fuse box to the fan switch, then a green and brown wire from the switch plug into the heater.
The brown wire also goes from the heater plug to ground behind the right kick panel.
I followed the wiring diagram and the black wire from the fuse box goes to a ground junction on the other side of the fuse.

Can anyone tell me how the fan is powered, and what should I test?
I only have a test light at the moment.

It seems odd that the switch worked before, and the wiring diagram is not making sense to me.