what is a trans axle fuse purpose?
Really, you're blanketing him depends entirely on whether he grows a sufficient winter coat or not. If he grows a nice coat, he'll probably be fine with the medium on only the coldest days (20). If he does not grow a good coat, you'll probably need to get a heavy weight. good luck :)
When you need a sweatshirt to be out at the barn, he needs the lightweight sheet when he's outside. When you need a coat and gloves to go get him from the pasture, he'll probably want his heavyweight. Consider clipping him so that he doesn't overheat under his blankets or get chilled after a workout. If you don't clip him, keep the cooler on hand. You'll want to use that so he's completely dry when he heads back outside.
A trans axle is the transmission. It's computer controlled so the fuse is for the trans axle computer.
Horses are big, so unless his piss is freezing before it hits the ground i think a big wool blanket will do the trick