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!

 

Check the Electronic battery sensor in the under the hood fuse box. Mine has been replaced 2x at 170k mi. This fuse sends the battery status to the car computer which tells the alternator that it needs to be charged. If this is not sending the info, the alternator/voltage regulator will not send the charge to the battery. Hope this helps!