[Vwdiesel] Finally need a new alternator? Burning through brushes.

[brian gochnauer]

Besides agreeing with what Mark said, I'd add that copper wire resistance
increases
with temperature, so yes, the alternator output like decreases as the
alternator heats up.

I'd measure full load and see what it's drawing, it would go along ways to
what the issues are.

On Wed, Jan 14, 2009 at 4:40 PM, mark shepherd <mark at shepher.fsnet.co.uk>wrote:

> Here's a guess at what is happening:
> If  a car is regularly hard to start, and so battery often starts the day
> needing to be recharged from a low level, then maximum amps come from the
> alternator for  relatively long time severely loading the brushes. They get
> incredibly hot, and also the more the rings wear, the more the  carbon
> brushes erode. Jump start a car then put the 'dead' battery on, and the
> alternator to battery wire can get quite warm and  even at idle the alt
> becomes untouchable.
>
> Mark
>
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> ----- Original Message -----
> From: "Will Taygan" <william at taygan.com>
> To: <vwdiesel at vwfans.com>
> Sent: Wednesday, January 14, 2009 10:22 PM
> Subject: Re: [Vwdiesel] Finally need a new alternator? Burning through
> brushes.
>
>
> >
> > 90 amp alternator.  I'm sure I'm putting stress on it, especially in the
> > winter.  I figured that was partially why I burned through brushes every
> > 6 months.
> >
> > Does the amp rating decrease as they age?
> >
> > The 94 Frankenjetta has a 1.6l with a serpentine belt setup and a 120
> > amp alternator.  PO set it up that way, maybe I'll reverse-engineer what
> > he did someday.  Great for running, PITA when I need to work on
> > anything, as it takes up almost all the space between the engine and the
> > body.
> >
> > Yellow top is to run the Espar diesel-fired heater an hour or so and
> > still have reserve for glow plugs and starting at -20F.  30 minute drive
> > home hopefully is returning a full charge.
> >
> > Will.
> >
> > On Tue, 2009-01-13 at 21:17 -0600, brian gochnauer wrote:
> >> >"Oh yeah, I've got a new optima yellow-top and pull quite a bit of
> >> >Amperage running the heater/radio/lights/vegtherm/etc. especially in
> >> the winter."
> >>
> >> How many amps are you pulling, how many amps is the alternator?
> >>
> >> Many people always forget;
> >> The size of the battery does NOT help when you have a large load over
> >> an extended time.
> >>
> >> The battery is like a cup of water, the alternator is like the faucet.
> >> If your load continually nears alternator capacity, it forces the
> >> alternator to run FULL capacity (AMPS) all the time.
> >>
> >> Battery size is for starting, not continual heavy loads.
> >
> > -snip-
> >>
> >
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> >
>
>
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