This evening on my way home the idiot lights started to glow faintly.I checked all connections to battery,behind the alternator,and to the big fuse.Everything was tight.The car only "glowed" once or twice then stopped. Is this the begining of a brush rebuild or regulator replacement? Any clues? Thanks,
Nelson
1990 240 DL

first my power window,then the power door lock,oh and yesterday the exhaust came down now this.Good thing it's spring!

My 1st choice would be the Brush/Regulator unit as suggested below.

I doubt it's the Alternator ground wire, as that is the final point in the ground path for the Alternator light.

Battery + voltage on one side should be opposed by alternator + voltage to keep bulb off. Bulb lights/glows with No/Low alt voltage, if it has ground path via small red wire to Alt, then thru regulator, brushes (and commutator), and finally the Alternator ground wire.
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Bruce Young
'93 940-NA (current) — 240s (one V8) — 140s — 122s — since '63.

Looks like it was the brush regulator unit. Replaced it today,1 1/2 hours of work and all is well. Thanks to everyone,
Nelson

go back to home depot get a torx set that folds you will need t 30, looks like swiss army knife it has different sizes. Email on the wheel on Vspeed

Often yes, Other things to check are:

The ground wire that runs from the alternator to the crossmember or block. I cannot stress enough, a visual inspection is not enough. Often the wire can degrade at the eyelet connector inside the insulation (got a $100 240 that way once). Pull on the darn thing enough to see if it will come out of eylet, but not so much that you damage a perfectly good wire.

Belt could be slipping or the harmonic balancer could be slipping. These usually make some sort of racket so you would usually notice.

Fuses...need I say more about care and feeding of those bullet fuses?

Finally, when all is said and done, when was the last time the regulator/brush assembly was changed? They only take 5 minute to change with the alt in the car and if you are wrong, you now have a spare.

Onkel Udo