hey guys,
i've had my alternator light coming on and off every now and then some trips its on 50% of the time. took it to the mechanics to have a look (and to do that bloody core plug behind the trans). anyway they couldn't fault the regulator but the oil-soaked belts were replaced- and the brushes were inspected but deemed fine. note that they couldn't get the light to turn on while they had it.
anyway, of course it still does it- but now there is another clue! i've noticed that when the battery light is ON, the aircon will surge (ie fan run faster) and if the headlights are on - they will surge also - along with the dashboard lights as long as the light stays lit.

could it be that an alternator could fail in a way that would overload the electrical system??

The ALT light basically has battery voltage on one side and alternator output on the other. When the alt isnt putting out volts that gives the light the 12V drop it needs to light up. I suppose theoretically the light could come on if the alt side went high but given that it would only be by a couple of volts I would have thought it would be very dim at best.

Get yourself a multimeter or voltmeter and connect it up to a power source in the car. Next time the light comes on see what the voltmeter is reading. If its above 13.9 you have a regulater problem (easy fix) if it drops below about 12.5 you have an alternator fault.

You can also check the alt when the car is stationary. You should have 12V on the battery with the engine off and about 13.5 to 13.9 volts with the engine running. Make sure you check your battery fluid levels as well. If the engine off voltage is low you may have a dud battery.

Hope this helps, just ask if you need more info.:D

my sisters barina was over charging and the light came on so had to get a new alternator

My old TR used to have the alternator light come on randomly, replaced the alternator regulator and it was fine. Think it cost $60 or less.

had da same prob with the light going on and off and of corse when it went to the mechanics it dint do it, however 3 months later it came on, didnt go off lost power to my H/U n me head lite went out almost completely. lol then light went off n all power was bk, i had a moody alternator woked when it wanted to so i presuming u gunna need a new 1 too.