My son attempted to change the battery in his car (09 Mazda 3 2.0) and some how crossed the
polarity. He says the battery sparked. The battery is in their correctly at
this point but his car doesn't turn over. Lights come on, air/heat, horn
and the dashboard but not the stereo or remote locks. We've been slowly
going through the fuses but it's pretty cold in Wisconsin so we haven't
checked all of them plus I have to work and he has classes.

I don't have time to keep checking everything with him so I'm helping by
doing research. I think he could of blown the starter or, from what I've
found, the fusible link. If it was the fusible link, wouldn't the dash not
work?

Each instance of a bad battery install seems to have it's own specific
issues. Most end up being the fusible link or a harness going from the
electrical system to the starter.

So this is were we are, any assistance, links, diagrams, or prayers would be helpful.

 

Only thing at this point is continue checking fuses and fuseable links.

 

We checked all the fuses, my son found that a 15 amp was blown which restarted the stereo, dome lights and key fob.

Now when we turn the key, we get a click and nothing. I noticed that right after we try to start it and then take the key out, there is a sound coming from the center right of the engine bay. It sounds like some sort of electronic hiss for a few seconds then it stops.

I'm thinking it's a blown starter or if the starter has a fuse in it then that's blown.

 

Take the starter get it tested.