It's important to know the direction of the diode in this trick is critical. You want the forward voltage drop added to the circuit. Backward will trick the alternator into thinking there's no sense voltage and not regulate at all.
I make this point because not every truck's fuse box is identical and if you build a gadget using one of the Tap-A-Fuse blocks using a visual reference from the Interwebz it's possible to have things oriented wrong or not fit. By turning it around like this I was able to leave a nice length loop on the wire for strain relief rather than trying to cut the plastic and re-seal everything.
For example on a 2nd gen Tacoma the Alt-S location required a different arrangement to fit against the side and for the lid to fit back on.
This was also a Schottky I tried in an experiment, which gave less voltage bump (about 0.3V) because in the summer having too high of a voltage is just as damaging as too low. A junk box 1N4001 was pushing up against 15V on my truck and holding that for hours on the Interstate in August can cause venting. That's very bad to do on an AGM since there's no way to put the magic juice back inside unlike traditional flooded types where you can add back water if you boil it. An AGM (or maintenance-free for that matter) will vent if you push them too hard to prevent over pressure and if it does that's a one-way turn down Ruined Street.
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In the end, though, I just ended up using a diode fuse from a Ford truck. The one I got was about 0.5V drop and works for my purposes almost year-round and fits inside the fuse box much cleaner. I just put the hobbled one in during long road trips in the summer now.
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