Electrical Battery light comes on and goes off

I've had this happen a couple times now. Not often, but it happened yesterday. Battery light came on as I was driving. I stopped, checked connections at battery posts, removed and re-connected terminals, tightened them up - nothing fixed it. BUT - multimeter showed 14.1 - 14.2 volts across the posts. So it seemed like nothing was wrong. And indeed, the car ran fine. It shut off and started again several times, no problem. It drove all the way to the auto parts store (to replace the negative terminal I broke while tightening), and then all the way home - no problems.

This morning, as I expected, the light was out when I started and didn't come back on when I drove to work. Battery tester on battery before start showed proper voltage. Load test showed operating within appropriate parameters. The only thing I did before the light came on was accelerate hard, shifting right before redline.

Last time this happened, I went under the hood and tightened the positive terminal's wire clasp - so where it grabs the positive cable, not where it grabs the battery post. Then it went out. I thought I had finally fixed it, but I guess not.

Any ideas what I should test? I mean, it seems to run fine, so I guess it's not exactly urgent - but I don't like warning lights in my car. It just looks bad, if nothing else.

jozsefsz said:

Ford alternators wear out at almost exactly 150k miles routinely. Usually they die with some sporadic warning-lights, and then it'll eventually completely die. If you're in that neighborhood mileage-wise, your alternator brushes are probably on their last legs. Time for a replacement.

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220k, actually. Is there a way to test the alternator first? To make sure that's really the problem, so I don't overlook something else, and just in case this is a replaced alternator already (I'm not original owner).