Actually, a weak older battery could cause this problem. But the first thing you need to do is clean all of the electrical connections between your battery, alternator and voltage regulator. Also make sure that you do this with both the positive and negitive connections. Many, many times I have seen someone take the time to clean all of their positive connections, only to have the negitive hookups be the problem. After you have cleaned everything, make sure that the drive belt is tightened to the correct tension, if it is loose, it will cause the alternator pulley to slip at idle. Once you have done both of these things, if it does not solve your problem, then start to look for a bad component. In other words, take the time to eliminate the stupid stuff before you replace something that isn't bad.

Nah the battery wouldn't be making the alt light come on. I'm more thinking problem could be the reg

Could be a weak bearing in your alternator.....mine was weak and eventually seized while i was driving. Also could be your battery playing up. Have your battery tested first.

Just after ya thoughts. My 1200 ute alternator light has just started to come on. I replaced the regulator that's mounted on the inner guard about a year ago. I have to rev it to get the light to turn off. But as revs drop back down after about 20 seconds I heard the regulator click and light comes back on. Do u think that the alternator is stuffed or could it possibly be the reg again? cheers