Chevy & GMC Vans

I am having a problem with my 95 Safari , little red battery on lower left instrament panel flickering when excellerating and voltage meter goes from 14 volts to about ten volts,ease off gas,battery light goes out and volts go back up to 14 volts???????(Happy Dads Day).this has been happening for along time.....with no apparent affect on starting?????

Belt may be slipping
Alternator on it's way out
Loose positive wire on back of alternator

The last one I had the same symptoms for a couple months. Was checking things out one day and found it was a little loose. Tightened it up, put another nut and lock washer on it, and haven't had a problem since.

Thanks jaxspl,belt is brand new,altenator only 2 years old,so I checked back of altenator,sure enough there is a black wire( negative I assume.)was 3/4 out pushed it back in to black palstic piece ,seems to have fixed it,is one able to see rear of altenator with dog house removed ,as I have not yet been able to tighten,removed protective rubber off positive side seems to be secure. Thanks again.......