Ok, go out to start the '97 mustang GT after work today seems normal starter begins to crank then all stop. Still have dome light, radio, etc.... No lights on the dash for self test. I go into the lab, grab a multimeter.. check the battery, 12.75 volts... blah. Get a jump car seems happy, dash voltmeter ok, no lights on after self test, great. Let it idle a little pull off. try to accelerate, bad stutters, ABS light comes on, voltmeter needle bounces a bit, check engine and battery warning lights flicker back and forth. Turn around, get into the parking lot, shut it off, get a ride home.
Come back with tools, MAC engine analyzer, etc in the mav. Jump it to get it going again. It's giving a good 4 amps trickle charge to the battery, looks good, current from the alternator looks good. Do the alternator test, in the good range (barely), check with all accessories on it's drawing a good 50-60amps. Decide to try and drive the car, it's better but the same symptoms are there a little. Decide I might be able to get it home then ride the bicycle back to get the mav. Here a whine I haven't heard before. It gets louder as I accelerate. Then it suddenly changes pitch, dash lights flicker, I turn around immedately back into the parking lot. Turn off the car, not enough enough juice to power the window back up on ACC. (hooked up the jumper cables to do that) Disconnected the ground wire, locked up the car came home.
My diagnosis, despite the encouraging tests is an alternator that's just about dead given the symptoms. If it were the battery, I would guess that the car would keep going just fine once it was jumped and I would at least make it until I turned it off again.
I'll be shoping for an alternator, remove the one and have the parts place test it as well. But does it seem like I am on the right track here?