Battery light issues..

Recently I decided to upgrade my alternator and do the big three to make sure my Ranger is supplying plenty of power. After the big three and replacement 200amp 6G from motorcityreman(as per the forum alternator page suggestion) I am now getting an intermittent battery light issue. I have no idea what causes it. The longest the light was ever on was for 30 seconds(some days it doesn't even come on and some days it will flash every minute) . I like my truck to be reliable so fixing this issue is a must.
Presumably I have somehow messed up a connection somewhere so I'll be getting someone to sit in the cab while I jiggle some wiring.
My truck is an, 01 2.3l xl.
How likely is it my alternator?
Any advice or comments are much appreciated.
Thanks Morgen,

Battery light circuit is the ON/OFF switch for an alternator.

An alternator is basically an electric motor used in a reverse application.
If left on(supplied power) it would try to turn, and of course couldn't, but would drain the battery trying.
Since it is directly connected to battery it needs an OFF switch, that's the Battery light circuit which only has power when key is on.

Light bulb 101: a light bulb works from power passing thru it, not just from "power".
If you hook up both contacts(sides) of a light bulb to 12volts what would happen........nothing, bulb would stay off since both sides are 12v, no power is passing thru the bulb.
If one side is 0v(ground) and the other 12v then bulb has power passing thru it so lights up.

Battery light circuit gets 12v from key being on, other side of bulb is hooked to alternator, which when off is a Ground, 0v, so bulb lights up.
When you start the engine alternator starts producing power, now bulb has 12volts on each side and goes off, no power passing thru it.
Actually 13.5v to 14.9v when alternator is working, but point is power on both sides of the bulb is now equal so light is off.
12volts from key being on turns on Voltage regulator in alternator, which supplies power to rotor and this turns on alternator, once alternator starts producing it's own power, this voltage is not required.

On Ford alternators this Battery light circuit wire is the Light Green wire on the 2 or 3 wire connector.

So battery light coming on means alternator voltage is dropping below battery voltage.
Battery voltage is stable at 12.5volts(approx.) if alternator voltage drops below this voltage, say 10volt then power would be passing thru bulb, and it would start to glow.
If it comes on bright then voltage at alternator has dropped close to 0v(ground).

So check this wire, if it should Ground/short battery light would come on.

Ford also started using Smart Charging, not sure if 2001 has that, and not sure of it's application to above system which has been used since internal and external voltage regulators were used.

Had a more hectic afternoon than I thought due to finals, I wasnt able to mess around with it today. Went for about an hour round trip and no light....
Thanks for the awesome write I'll be checking it out tomorrow morning for sure.

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I read through this because I have the same issue...and wasn't sure what wire was the problem...now I know to check the green/red stripe...and I took a look at it today...appears to have been spliced at some point but will have to check it more closely tomorrow.

At first I thought was coming on because the battery kept draining...and I can't remember it being on last year when I first got the truck...been chasing wiring issues for a while now...

My issues seem to have subsided, I havnt had the light show up for nearly 2 weeks now. I checked all of my wiring yesterday and didn't see anything looking bad. I'm just wondering now if it's my alternator that could be defective.

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And wowser...mine went out today for the first time in four months...I did need to charge the battery last night because it was drained when I tried to start it...it came on after I turned the engine off and started it again...went out after a bit of flickering...

Pretty sure it is a loose wire...but in the ignition...