Just to be pedantic, the fan speed controller does its thing by pulse width modulation, not resistance variation.
The loom goes from one footwell, through the bulkhead, past the fan and back through the other bulkhead (if it’s pre- 2006). Difficult to remove, so I spliced on a replacement “lump” to the old loom. Post change-over units are the same as pre. Only the loom arrangement is different, and the wire colours are the same.