Alternator about to die?

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Alternator about to die?

Post by risk » Mon Sep 11, 2017 3:07 pm

Converted my 67 from generator to alternator a few years ago.

Been great and no issues til the other day.

Cold start, alternator light stays on but gets dim when revving the motor. After a minute, maybe less it goes out.

Belt is tight, and checked all connections no problems there.

Is this a sign that the alternator is about to take a crap?

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Re: Alternator about to die?

Post by Marc » Tue Sep 12, 2017 1:52 am

I would pull the brushes out and inspect them (and the sliprings). Could be contamination where they contact or insufficient spring tension due to worn/broken brush. I saw one once where the brush lead was fouled on the holder frame which limited the travel of the brush, all it needed to fix was to reroute the lead.

Are you running any kind of relay off of the alternator D+ (e.g. for the fuel pump)? If so try changing it out, it could be drawing too much control current and dragging down the voltage present at the warning lamp.

The original German-made AL82 had the regulator mounted along with the brushholder; the Brazilian-made version puts it in the void space at the fan end of the alternator, making it much more involved to replace (have to remove the bearing plate to access it). Brushes and regulators for both versions are available, just a little hard to find sometimes. Check for any radial play in the fan-end bearing, if it's getting sloppy it may make more sense to replace the whole thing rather than renew the brushes/regulator.

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