Yes there are many grades, materials, etc. used for motor brushes. In
addition there is also the type of use. The voltage regulator controls
alternator output by varying the magnetic field (current) of the rotor as it
spins in the stator. Since you are now using the alternator to charge
additional batteries it has to regularly work a lot harder. Using the
adjustable regulator to raise the set voltage makes things even worse. To
add to the dilemma the original brushes are somewhat hard and they also wear
the slip rings on the rotor. New brushes will quickly get chewed up as they
will try to go into those grooves. Also at that mileage the rear bearing or
the insert that holds it is most likely shot allowing the rear of the rotor
to move around. As the rotor loses center the alternator loses efficiency
and again more current is passed in the rotor to compensate.

The main point is that worn brushes are also an indication that it is time
for the alternator to be fully serviced. Having the bearings crash also
means no water pump so you are now stranded. Also since the failure will
usually occur on the highway you have to consider the effect of the engine
overheating by the time you realized what is happening.

Dennis

-----Original Message-----
From: Vanagon Mailing List [mailto:vanagon@gerry.vanagon.com] On Behalf Of
Rocket J Squirrel
Sent: Monday, August 22, 2011 5:29 PM
To: vanagon@GERRY.VANAGON.COM
Subject: Alternator Brushes Wore Out Pretty Darn Quick

Buried in my post from yesterday (about an intermittent charging issue) is a
question about the wore-out brushes on the voltage regulator.  The
reg/brushes can't have more than 20,000 miles but were worn to nubbins, less
than 1/8'' long.

Fortunately I had my old voltage regulator which probably has 70,000 miles
on it and its brushes were much longer so I swapped it in and the charging
system is working fine.

What can cause brushes to wear quickly?

Do different brands of brushes wear differently? (The ones that wore out
quickly were on an aftermarket adjustable voltage regulator, my old one with
the still-long brushes is a factory type).

Could something have happened within the alternator to speed brush wearing?

--
Jack "Rocket j Squirrel" Elliott
Bend, Ore.
1984 Westfalia. A poor but proud people.
1971 "Ladybug"-brand utility trailer ca. 1972 from a defunct company in San
Clemente, Calif., now repurposed as The Westrailia.

Sent from my kitchen.