QUOTE (altons4439 @ Oct 25 2009, 05:59 PM)

I have a 2001 Eclipse GT. My battery completely died on me one day and when I took it in for repair, they told me that my alternator was dead which in turned killed my battery. They then replaced both the alternator and battery. When I left the mechanic, my battery indicator (along with another indicator, can't remember right off) were flashing irratically on my dashboard. I took the car back to the mechanic and was told that I had a bad alternator, so that put a new one in. Problem didn't go away, so then I was told that my harness is probably bad and needs replacing. I asked if I could drive it as-is without hurting anything and they told me yes. I did this until one day my car wouldn't start because the battery was dead again. When I took it back to the mechanic, they told me that everything looked good (battery, alternator and harness), now they're thinking the computer might have a problem. They recommended taking the car to the dealer at this point.
I did my own measurements at the battery terminals to understand what is going on. This is what I found:
When idle - ~13.8VDC
When above idle but below 2500 rpm - ~12.3VDC
When 2500rpm and above - ~13.99VDC
Sometimes at idle the voltage is less than 13V.
Based on research, all indications are that its my regulator. The regulator is built into the alternator and they changed it twice, so is it likely?
Could I have a bad battery?
One other strange behavior: 90% of the time I can drive the car normally, park, turn off the car and come back and it'll re-start as if nothings wrong. But about 10% of the time when I go to re-start, I get virtually nothing, not even a weak attempt to turn over. I then jump it off and it starts ok again.
I plan to take it in for another repair attempt, but I would lke some indication of what might be happening. Hope someone has an answer.
if they replaced both the alternator and the battery, it must be something else... sorry I cant help you out there.