I had a voltage gauge on my turbo timer and I noticed that the alternator really doesnt generate much power at all at idle. But once the rpm is over 1000 rpm, the voltage would jump and settle perfectly. My alternator works fine, and hasent caused a problem, but I generally would have to give it a little rev once I started it to get the voltage up. It would run just a tad rough until I gave it that little spike. Then the alternator would generate power just fine. But I could achieve that same problem if I was cuising, and just put the clutch in, and come to a rolling stop. But If I came to a stop using a bit of engine compression and downshifting, the voltage would never drop.
And the voltage gauge is surprisingly accurate. Ive compared it to my multimeter.
You could also be draining the battery through a bad wire or something too.
