Alternator to be changed soon ?

[Nova 3 GT]

For the last 2 days, I noticed that my voltage behaves strangely.

When cold before starting, battery voltage is at 12.75V.

After starting, it goes to 14.0V-14.1V which I presume that this is the normal charging voltage.

10-15min later at idle, the voltage reads 13.2V. :whoa

However, it goes back to 14V when I'm driving around.

What could be the cause of these fluctuations?

FYI, it doesn't matter if my A/C is either on or off

[staax]

Likely fine, I know mine fluctuates between 13.3 - 14.0 when the car is on.

You'll know it's bad when it stops charging periodically or stops completely.

[Nova 3 GT]

Oh ok. That means as long as I don't see battery voltage (12.6V-ish) when the car's running, my alternator is still fine. Whew!

[staax]

Normally when you're alternator stops charging your battery light will turn on. If it stays on the alternator has failed and you've got about 10 mins before you're dead on the side of the road.

[DLYDRVN]

Mine is also in the 13.8-14.0v range, but my understanding is that auto voltage should be 14.4V at Idle, minimal load. MY Ms2 and Rx8 all run 14.4v. I've got a yellow top and full big 3 upgrade AND a kinetik power cell. Been thinking about upping my alt for that reason alone.