New alternator now wont start

I installed new alternator today and now the truck want start. It wont turn over.... what did I do wrong?

 

It always helps when the trucks in neutral stupid!!!! I had my blonde moment of the day.

 

Another issue I had was I bought a new pully to put on even though dealer said I could use the old one, but after hand tightening it still had like a half in of space between it and the alternator so when I tried tightening it that thing inside the alternator just kept spinning... I didn't know what to do so I just installed the alternator with the pully and figured after I put the belt back on it would be easier to tighten LOL

It didn't work it kept spinning... So I ended up taking a screw driver and putting it in the alternator to hold that thing from spinning while I tighten it... I know they say you aren't supposed to do that...

I watch a video online afterwards and a guy did it using impact wrench...

I've got an impact, had I of known...

Is using the impact the proper way that pully is supposed to be tighten on the alternator or is there another way?

 

Yes, your doing it with the impact if I understand correctly?

 

Still having starting issues. Installed new starter last month, alternator yesterday...

Every morning truck doesn't wanna start.. Just clicks when I go to start...

Paid peterbilt $300 a little over a month ago to check everything which they claim was good.

In the morning after it wont start I'll turn my apu on, then the truck starts right up... My batteries are 18 months old maybe I need them replaced now?

All connections appear to be fine... Is it possible that Big Black fuse that's in the fuse box I thinks it's called main line fuse or something like that needs replaced?