well the alty on my 96 gle might be the stock one, as ive never changed it in 3 years, but when the car is on, it puts out between 13.5 and 13.9 volts to the battery. then the battery, which is a yellow top optima with 750 cold cranking amps, that always stays at 12.3 volts with barely 720 amps. would this be my alty going out slowly and not properly keeping the battery charged??
im asking because now its gotten cold to the point were it is a little slugish turning on. . . .

 

Could be a number of things. First off I hear those Yellow Tops are hard to kill so lets doubt its your battery, im gonna go ahead and say you probably need to reground, and also as it gets colder its going to be harder to start and such; i don't know the science behind it though so if anyone does please feel free to educate us.... These alternators are NOTORIOUS for going out, ESPECIALLY Reman's Do Not in the event you replace your alternator get a reman. 13.8-14.5 is typically the area you want to find yourself voltage wise... Can i assume you have a system? As yo udo have a Yellow Top?

 

If all that you really notice is slow start it could be your starter. It's fairly easy to remove it and get it tested. If your headlight brightness appears to be fine your battery and alt are probably OK.

 

The charge warning and possibly your brake light will usually turn on if your alt is going. Those readings you provided may be normal. I would expect the battery to read higher when the car is running and the alt is charging.

 

well the battery and brake light arent one. i have the yellow top because at one point i did have a huge system in my car, about 2000 watts. so at that time i attributed the slightly lower volts to the system that i would play all the time. but the system has been off the car since july!!! and as for grounding, i have a four gauge grounding kit from the main points on the motor and under the hood chasi directly to the battery ground.
the starter has been replaced before, i did it myself, so i know how to swap it out pretty fast . . . and as for getting another alt soon, maybe, but the only ones i really find are all remanufactured!!!
one thing i havent done yet is probably clean up the stock grounds in the car.
but thats about it

 

Ive gone through 5 Remanufactored Alternators. My system is only 715 Watts RMS.

 

13.5v - 13.9v charging volts is fine, there's nothing wrong with your alty.
12.3v resting seems OK, 720 amps on a 750 rated battery is OK, although showing it's age.

 

Grab your multi-meter, and put it on.

Turn on your fan to high heat, headlights on, radio pumped up, rev the car to 2000 rpm, and check if your headlights dim while braking.

Should your volts keep dropping, your alternator cant hold the charge and is on it's way out. Less than 13 v, bad alternator.