Not sure what's on with this.

Once my RPMs reach about 3000 - 3500 the voltage gauge drops from 14 to around 9 or 10. ( The voltage needle switches from a 12:00 position to a 10:00 position )

Also noticed the voltage gauge bounces slightly when I use my turn signals.

Any insight would be great. Thanks!

 

First I'd check all of the connections and if that doesn't fix it, I'll pull the alternator out and get it tested.

 

This plus check the belt and tensioner.

George

 

This was my thought, too. It sounds like it could be belt slippage.

 

If idle voltage is good and belt doesnt squeal...Worn brushes in alternator. Guarandamtee it. A pretty easy job.
Ford 80 amp were notorious for this and it made for cheap replacement alternators For my kids' mustangs if diode or regulator failed. Used alt plus brush kit plus lube equal rebuilt for cheap