What fuse protects this circuit?

I have determined that the power for the M4 fan comes from the center terminal of the three-terminal connector with two red and one brown wire at N65. But I can't figure out what fuse protects this circuit, or where it gets its power.

I unplugged every fuse in the boxes under the hood and under the rear seat while watching the voltage on this terminal, and none of them cut it. I did not pull any fuses from the box at the side of the dash, which seems to only power lamps.

The placard in the underhood fusebox says that #20 is the fan fuse, but my fusebox lacks any fuse socket marked 20 (or the spare, #19).

Note that this is an early 210, and the M4 circuit differs from later models.