AC Pulley Slides Out
 

On my 2000 4 cylinder toyota camry, the ac pulley slides out and hits the car frame. When it is in, the ac works fine, when out, it doesn't. I can push it in and it will go a few days and run fine.

I can feel a hole in the middle of the pulley, so I suspect a bolt is missing. Is there a bolt missing, that I can replace, or do I need to take it to the shop? (I am somewhat mechanical)

Any suggestions will be appreciated.

Thanks,
Amy B.