RE: Alternator Light

["tofunit" <tofunit@yahoo.com>]

Hi all,

I just happen to have starting problem yesterday, and tought
that my solving of the problem could help others....

Sunday, I turn left on the street and all the power cut down
and came back!!! It was very strange, I thought of a wire/Battery
problem, but was okay after... Yesterday, went to take a coffee place
with my gf, and when we left, I had problem starting my car!
Just like if the battery was almost dead... then nothing as if
the wire to the battery was cut! So I was stuck there and no tools
with me :( and no boosting cable, whatever my gf went back to the
coffee place to ask if they have some tools.. the coffee place is
called "Garage restaurant", but it's not a Garage :) Anyway, I could
get something to unscrew my battery connector!

The connector on the battery pole was tight enough, but the two
screw that hold the + wire on that connector was not tight enought,
and by moving the wire the connection was going on and off!

As many of us, I put some more wires under the metal pieces that hold
the big + wire, just like the sound system, alarms, etc.. well It was
making an additional gap, and I thought removing them between the
metal pieces that hold the + wire to put them over the metal piece
and use them as spacer to put more pressure on the big + wire...

Well I bought some boosting cable, always useful! And my friend
came to boost my car and took a second to start the car!

What it was good to see now is the voltage was 14V, usually it is
around 12v and if I put the light on, the fan, the defrost, etc...
was almost always under 12v and near 10v.. But now the voltage
was 14V...
I never saw that on my car before!!!! And with all light on, fan,
defrost, etc... still over 12v...

So I think it's a good thing to check if you have a low voltage
on the meter of your car :)

Joel

-----Original Message-----
From: owner-scirocco-l@scirocco.org
[mailto:owner-scirocco-l@scirocco.org]On Behalf Of Fry, Larry
Sent: Tuesday, November 06, 2001 9:13 AM
To: photo@intrex.net; scirocco-l@scirocco.org
Subject: RE: Alternator Light


So....what all this means is that those of us experiencing this phenomenon
need a new alternator, or at least, a new voltage regulator.
 Right?

Larry  sandiego16V

-----Original Message-----
From: Bill Collins [mailto:photo@intrex.net]
Sent: Tuesday, November 06, 2001 5:41 AM
To: scirocco-l@scirocco.org
Subject: Re: Alternator Light


The initial excitation comes not only from the permanent magnet, but also
from current flowing through the warning light.  On many VWs, this light is
an LED, which allows much less current to flow than a light bulb does.  I
assume this is part of the reason this seems to be a VW only problem.

Bill

>I'll go into 'the details' for marc (p.s. marc, you know all this stuff
>already).
>
>An alternator has rotating winding (armature), as well as stationary
>windings (stator).
>     Current goes through the armature winding (via the rings/brushes many=

of
>you have seen), making it one big rotating magnet. This magnetic field is
>felt by the stator windings, causing them to produce an AC output. This AC
>is then rectified (converted to DC) and sent out to your battery. The
>regulator 'senses' the DC output voltage and varies the current to the
>armature, varying the intinsity of the field, thus varying the output
>voltage. You may be wondering 'what the heck does the regulator part have=
to
>do with the light staying on till i rev the engine*&#$^@', here's your
>answer:
>     Picture the car off, alternator is not spinning, nothing 'generated'=
by
>the stator, since the armature is not rotating. The reverse is true here:=
no
>generated voltage, regulator has no voltage to make the armature current
>from (dont go thinking it has battery voltage, the battery cannot supply
>current TO the alternator, since it would be going backwards through the
>rectifier (just go with me on this, it doesnt work that way)). Compared to=

a
>gas grille, the gas is off and there is no flame.
>     Now, you start your car. Belts start spinning the armature. Wait a=
sec,
>there is no armature current, and no stator voltage to make it. So now,=
"The
>gas is on, but there is no flame". What the heck%*&@)%. How does this thing

>ever get going you might wonder???
>     Answer: There is a small magnet built into the center of the armature
>winding. It supplies the initial field, just enough for the stator to
>generate some voltage (our "spark"), just enough for the regulator to send
>current to the armature and 'jack up' the output voltage to the 14VDC we're

>all happy to see from a working alternator. The whole process is called
>'flashing the field', which is why i related it all to a gas grille.
>     Question #2: Why does my alternator do this flashing light thing now,
>when it didnt do it when the car was new?
>     Answer #2: Several possibilities:
>         1. Magnet is getting weak: rust, heat cycles (remember, from high
>school, heh), vibration.
>         2. Rectifier diode(s) are open: the stator on our alternators are=

'3
>phase AC generators' to rectify this type of AC down to single phase DC,=
you
>need a group of 6 diodes. 3 phase systems are high reliability (the entire
>power distribution system on my submarine was 3 phase), portions of them=
can
>totally not work, but there will still be at least some output. 1 or 2 of
>these diodes can be broken causing the DC output to be weakened. While this

>may be ok once the field has flashed, it will require a higher rotating
>speed to get it flashed to begin with.
>         3. Stator field winding open: one of the 2 windings could have an
>open wire. The effect is the same as open diode(s) associated with that
>field.
>     You can 'knock out' one of the 3 phases and still get nearly 50% power

>output. Thank VW for overengineering everything, since your scirocco can
>probably still run just fine on the 3 phases.
>Hope this info helps everyone.
>Al
>

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