[Vwdiesel] Update 92 ECO Diesel Alt light on

Nate Wall NWall at envasns.org
Mon Jan 28 13:05:37 EST 2002

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<<<<<[ Picked text/plain from multipart/alternative ]
I tightened the belt, and the light now stays on all the time except at idle.
So I thought I would check it with a meter. At idle it is charging at 13.5
volts. When I increased Rpm's voltage dropped down under 11. I pulled the
alternator off, and removed the brush plate. One of the brushes was . 5" long
and the other was almost nonexistent. I also noticed a burnt ring of plastic,
floating on the contact ring of the stator. I take it that burnt ring is the
aft bearing retainer. Another thing I noticed the area that the brushes ride
is recessed, as if the brushes wore a track in the area. During past brush
changes I am use to seeing this area flat, with some discoloration that can
be removed with sandpaper.

So where can I go from here. I checked the local auto parts places and have
gotten prices between $195, and $256. What other VW's would have this Alt? It
says 90a, on the tag. I was going to check the local junk yard.>>>>

The old alternator I had had a "channel" worn in the copper slip rings where the brushes ride.  Although not ideal, this should not prevent the alternator from charging.  See if the rear bearing is loose by rocking the front pulley up and down, to try to get the rear bearing to move.  If the carrier spun in its housing, the rotor shaft will have lots of up/down play on that end.  If it gets bad enouugh, the rotor can contact, and cut into, the field coils.  This may be what happened, and if a field coil shorts because of this, I bet it don't charge no more!  If there is no play, replace the brushes for $5 and see if it works.  Sounds like they are worn out.


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