I discovered, after instantly blowing the 2A fuse in the “Auxiliary DC jack”, which we affectionately call the “cigarette lighter” jack, that 1) all the detailed information about the three fuse boxes and their fuses lies in the Owner’s Manual, (pages 7-33, 7-34 in my book) and not the Yamaha service manual, and 2) you’d better forget intuition, because when you assume the 2A fuse is in the location you’d believe, i.e. Fuse Box #2 and perhaps would be in location 6 or 8, since they are called “Auxiliary fuse” (1 and 2) – you would be wrong. The correct fuse is in Fuse box #3, and it was “Terminal fuse 1” location, (4). The label, inside the cap, showing the fuse ratings, was upside-down on my bike, leading to further confusion. The drawing in the Owner's manual is correct. There was a spare fuse in box #3.
 
By the way, the accessory I was trying to use was a small air compressor, not designed for a motorcycle, and apparently draws far more than 2 amperes.
 

Thanks for the info.
 
I have fused wires with SAE connectors from the battery to run my lights, with a join under the seat to power my compressor.
Rewired a $12 compressor from the local autobarn with mated SAE connectors (need to get polarity correct).
It works well.
 
A few of the Dual Sport guys around here use and swear by Anderson plugs for the same uses.
It's sort of a standard with them, so they can all share a compressor/coffee grinder/whatever.

Similar here suncoaster. I have a SAE connector under the seat, connected to the battery which I can use to charge the battery or connect a compressor to.

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Thanks for the info. Can't imagine how frustrating that was to discover... Actually I can lol.

These days nothing is intuitive any more. What sense does it make to have a 2 amp auxiliary power connector? 10 Amps would require just a $1 more wiring and fuse.

I still use a foot pump and bar of chocolate. I need a chair sometimes too! 

I blew a fuse the other day using my compressor ??‍♂️So where is Fuse box #3, and it the “Terminal fuse 1” location?

Awesome.  Thank you!   I was pulling my hair out on that one.   

That’s so funny I played that game the other day. I ended up getting the multimeter and still getting stumped before I just ended checking all 2amp fuses.