I cannot pinpoint the exact cause of the issue, and its leaving me to believe its the internal regulator in the alternator.

At idle, I will get around 12.5V.
At highway speeds, I will get around 12.5V.
Sometime, I will get 15+V at highway.

It corrects itself randomly for whatever reason. I am fairly familiar with alternators, and amperage going up with spin speed, and no way I should be getting that low voltage at 2000 RPM (IMO).

Once again, I can't pinpoint it. I tried to turn the radio on and off, and responded once in voltage, but not again. Applied the brake - responded in voltage once, but not again. It is all random.

I have a radar detector with a built in voltage reg, and this is what alerted me. I double checked with a digital volt meter.

Any insight is appreciated. Thanks!

 

Alternator sounds like a likely culprit...

 

Changed the ALT - Still the same issue (pissing me off). What else could it be?

 

did you buy a rebuilt one? Perhaps it's a bad cell in your battery. Get it tested and get your old and new alternator tested.

 

It's a low mileage OEM one. I have a brand new battery and it occurred with the old battery as well.