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Date:         Mon, 22 Aug 2011 18:04:52 -0400
Reply-To:     Dennis Haynes <d23haynes57@HOTMAIL.COM>
Sender:       Vanagon Mailing List <vanagon@gerry.vanagon.com>
From:         Dennis Haynes <d23haynes57@HOTMAIL.COM>
Subject:      Re: Alternator Brushes Wore Out Pretty Darn Quick
Comments: To: Rocket J Squirrel <camping.elliott@GMAIL.COM>
In-Reply-To:  <4E52CA16.3070201@gmail.com>
Content-Type: text/plain; charset="US-ASCII"

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.


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