intermittent alternator light? 89 930

[tiorio]

I've got an intermittent problem with my alternator light. Basically, it comes on for 2-5 minutes, then goes off. Sometimes it's on when I first start up and then goes away, sometimes it shuts off (as normal) when I start the engine and then after 2-10 minutes of normal driving comes on again. Sometimes it stays on until I shut down, sometimes it goes away of it's own accord.

I haven't had a chance to test anything, not even hook up a voltmeter, too much work but I thought I'd throw the line out anyway to see if anyone had a similar experience.

One last thing, belt is in good condition and has proper tension.

[john walker's workshop]

most likely the brushes in the regulator are worn out and barely making contact with the commutator ring in the alternator. the ring is generally worn out too. replace with a complete alt/reg unit if that's the case.