Robert K. Kuhn
CRX Owners Group President (http://www.crx.org/southcal)
1990 Honda CRXsi (http://www.hooligan.cc)
ICQ # 3714283 (nickname: godzilla)
Alpine Drive (San Diego County) - February 8, 2003
http://www.crx.org/southcal/events.html
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To: [EMAIL PROTECTED]
From: Citizen Kang <[EMAIL PROTECTED]>
Subject: RE: [hooligan racing] Dual Battery
Date: Fri, 24 Jan 2003 18:09:15 -0800
Reply-To: [EMAIL PROTECTED]
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Get a second opinion.
If their books say that your car came with a 51 Amp alternator and it
only puts out 40 Amps when tested in the vehicle, that doesn't mean that
there is something wrong with your alternator. You see, alternators use
regulators to regulate the voltage they produce. Inside the outer body
of the alternator are three sets of windings -- essentially long wraps
of lacquer-coated copper wire. As a unit, these windings are called a
"stator". The central rotating section (called an "armature") inside
the alternator functions as a big magnet and the magnetic field it
produces bisects these field windings, inducing an electrical current
into them. Alternators are really "alternating current generators", and
as the magnetic field spins around, it creates a current flow in each
set of windings that rapidly reverses direction. Just like AC current
for your home. There are two diodes incorporated into each of the three
windings. Diodes allow current to flow in only one direction. When the
current flows in one direction in one of the windings, one diode blocks
current flow while the other shunts it off to the rest of the regulator
circuit. When the current flow in that particular winding reverses (ie:
when the armature rotates a few more degrees), the diode that was
blocking the flow now shunts the electricity to the regulator while the
other one blocks the current flow. Such a set-up is called a bridge
rectifier and it is the heart & soul of any device that converts AC
power into DC power. If one of these diodes burns out, you effectively
lose the power producing capability of the entire winding. Such a case
is often evident if you notice a high-pitched whistling noise coming
from under the hood that wasn't there before.
But these windings aren't wired in completely isolated from each other.
It is rather complicated, but "Automotive Electronics 101" says that if
just one of these six diodes burns out, you lose the power producing
capability of TWO of the three windings. As a result, if one of these
diodes blow, your maximum alternator output should be reduced to a mere
33%! So, if you have a big domestic alternator capable of producing 100
Amperes according to the manufacturer and a fancy machine says it is
only putting out 80 Amps, there is nothing wrong with the alternator.
Rather, you probably have a load somewhere in the system (like leaving
your headlights on when performing the test), bad wiring (excessive
resistance in the charging circuit can cause a voltage loss -- which can
result in a current loss), or maybe even a bad battery (a misbehaving
battery will not allow you to perform a truly accurate test of your
charging system).
A proper test will be able to tell you the charging voltage, charging
current, and diode pattern ("good" or "bad") of your car's alternator.
You should disconnect the isolator and take it and your secondary
battery out of the loop while testing to make sure that it isn't
contributing to any bad readings. Some garages use massive carbon-pile
variable resistors to put a load on your electrical system (the
venerable Sun "VAT-40") and not too many techs really remember how to
use these things nowadays. Testing equipment today has come a long way
and hopefully most shops have access to these more accurate tools. Any
shop with a relatively new engine analyzer (or "scope") should be able
to perform an accurate test, as should any shop that has either
cart-mounted or handheld digital testers. We just got a really nice
handheld unit from OTC that even our cashier can use (sorry Carla)!
So get a second opinion.
PS: "Current" (or a lack thereof) doesn't turn your alternator light on
or off, voltage does. If the voltage exiting your regulator isn't
within the 12.2-14.5 volts range, the light will turn on. If for some
reason your voltage regulator dies and stops regulating the voltage
coming from your alternator, you might experience a voltage reading in
excess of 14.5 volts (sometimes as high as 16V!). This is bad news for
your delicate electrical stuff and the warning light knows this, so it
turns itself on. If your voltage drops below 12.2 volts, this is a sign
that the alternator really isn't producing any voltage at all and the
reading being observed is actually the voltage in your battery (which
will continue to drop until the battery is exhausted). This also turns
the light on. Finally, a bad diode can also turn this light on. The
above voltage numbers can vary widely among vehicle manufacturers and
are simply my best guess...
> -----Original Message-----
> From: Jason M. Tyler [mailto:[EMAIL PROTECTED]]
> Sent: January 24, 2003 9:43 AM
> To: [EMAIL PROTECTED]
> Subject: [hooligan racing] Dual Battery
>
>
> OK -- After about a week, I finally broke down and took the
> car to a shop to
> try and figure out why my alternator light comes on when attempting to
> charge to batteries with a battery isolator installed.
>
> Prior to taking it in, I tried the following:
>
> Checked and adjusted belt tension.
> Replaced the alternator brush (which has the regulator
> built into it).
> Replaced the old ground cable on the stock battery.
> Replaced the old positive cable on the stock battery.
>
> The shop that I took it to did a load test on my alternator
> and it turns out
> that I'm not getting the full amps that it's capable of
> producing. I guess
> it was producing just enough to keep one battery charged.
>
> I have a choice to make -- do I replace the stock alternator
> with another
> stock alternator or do I invest more and get it rebuilt to be
> a high output
> alternator (which is at a pretty significant cost).
>
> Thoughts, comments, ???
>
> Jason M. Tyler [[EMAIL PROTECTED]]
>
> 1968 Hooligan Racing (wannabe) Bug
> 1990 Honda Civic/Si
>
> I live with Fear everyday. But sometimes she lets me race -- No Fear!
> hooligan racing, usa (http://www.hooligan.cc)
>
>
I live with Fear everyday. But sometimes she lets me race -- No Fear!
hooligan racing, usa (http://www.hooligan.cc)
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