Question: how do you know if your alternator belt is loose?
Answer: 1# Squealing Noises. A squealing noise for a few seconds when starting the engine is a surefire way of telling that the alternator belt is slipping. ... 
2# Battery Warning Light. A loose alternator belt means that the battery does not get adequate power. ... 
3# Blinking Lights. ... 
4# Dead Battery. ... 
5# Stalled Vehicle.