Idiot lights all came on. Opened hood, one alternator belt partially shredded and the 2nd popped off. Alternator is loose.

I can spin alternator and fan pulley.

Is there a way to tell if either the alternator or fan clutch pulley are locking up without putting new belts on?

 

if they spin, they aren't locking up.

Its possible the belts were too loose, its also possible the alternator rubber mount bushings were really shot so everything was crooked.

 

nothing new, see it all the time. that's how you know the belt is bad.

spare belts in the car + 12 and 13mm wrench and ratcheting 10mm and flash light.

 

If just belts were bad, then why is alternator loose

 

loose in what manner?

 

How old were the belts? Were they improperly torqued/tightened?

When was the last time you inspected the belts for cracks and such?

Was the car squealing at all before this? It's hard to believe that the belts just catastrophically failed without notice.

 

Alt. should not be loose, belts or no belts! Being loose would certainly cause the belts to come off or break as they did...