2008 Fit 80k miles, charging system light came on. Replaced the battery (failed battery check after getting external charge) but the battery light is still on. Local auto parts place ran alternator check but couldn't get any output. They thought there was an in-line fuse that may be blown but didn't know where. I haven't found a diagram...any help on what/where that may be?

I've checked the 80amp fuse at the positive battery terminal, the 80amp fuse in the underhood fuse box. Anything else?

 

At that age, it couldn't hurt to take apart and clean the conections-especially the ground to the block from the neg terminal on the battery. Shaky grounds can make all kinds of weird problems. Just make sure you have the radio code!