Hello! Long time lurker, first time writer.
I've had my 2013 Fit Sport (75k miles now) since the beginning, and here are the random (and now progressing) electrical issues I've noticed.
4 years old: Noticed that sometimes a cabin light comes on by itself after I lock the doors, resulting in a dead battery (I NEVER use these lights but for the first couple years I assumed I was accidentally pressing them, but I'm 99% sure they are coming on on their own. Always just one of the front lights comes on).
6 years old: Got new tires and when I left the parking lot, I noticed when I put my turn signal on that the turn signal light flashed much more quickly and didn't make a sound. The people who installed the tires said it wasn't possible that they caused the issue. I also now have noticed that the turn signal makes the correct sound and flashes at the correct pace but ONLY when I am not braking. When braking, it flashes quickly and is silent.
10 years old: On my last road trip I noticed that when I use cruise control and then turn my right turn signal on, the cruise control is canceled (not completely turned off, but it decelerates and i have to press "set" to get it to turn back on).
Now the AC light also doesn't want to stay on.

What's going on? Any guesses?

 

If the cabin light is set to turn on automatically, then the computer likely thinks the doors are or were opened.
The non-replaceable light flasher relay inside the dash unit will hyper-flash when LED lights are installed or when load is too low.