the other day my battery light came on my truck so i took the edge and switched it over to measure BAT Voltage...On friday it was at 11.7 when driving but at idle it increased to about 13...i shut the radio off but that didn't seem to affect anything...I was driving it yesterday and its down to around 11.2 whether im idling or driving it doesn't matter...I guess what im asking is is my battery going dead or is it my alternator??

 

I would say have the alternator checked at a napa or the likes. More then likely is you will have to replace the battery at the same time, as the alternator has been abusing the battery with poor charging.

 

What SSCULLY said, sounds like the alternator brushes are chattering.

 

thanx guys...took it to oreilly's and the alt was bad