Date:         Sat, 24 Apr 2010 13:35:51 -0500
Reply-To:     John Rodgers <inua@CHARTER.NET>
Sender:       Vanagon Mailing List <vanagon@gerry.vanagon.com>
From:         John Rodgers <inua@CHARTER.NET>
Subject:      Re: alternator installation
Comments: To: Tom Hargrave <thargrav@HIWAAY.NET>
In-Reply-To:  <034401cae3da$ed457bd0$c7d07370$@net>
Content-Type: text/plain; charset=ISO-8859-1; format=flowed

Like I said - it's been a long time. Good to get that refreshed in my
mind about alternators.

John

John Rodgers
Clayartist and Moldmaker
88'GL VW Bus Driver
Chelsea, AL
Http://www.moldhaus.com


On 4/24/2010 1:21 PM, Tom Hargrave wrote:
> John,
>
> You are absolutely right if discussing a generator. The field is composed of
> 2 or 4 electro-magnets mounted to the outside shell and the magnets will
> hold enough magnetism once magnetized that you don't need an external
> battery for the generator to re-start.
>
> But a alternator rotor retains so little magnetism that it usually takes a
> small amount of current to start one up. That initial current is supplied
> through your GEN dash light. Then, once the alternator starts up a smaller
> of two diode bridges inside the alternator provides current to the
> regulator. The larger diode bridge provides current to the car's electrical
> system.
>
> BTW, this is why your GEN light stays on when your alternator or regulator
> fails. The alternator rotor is no longer receiving excite current from the
> regulator and it continues to draw the small amount of current through your
> GEN light. But the current is not enough to drive the alternator to put out
> any real power.
>
> Tom
> www.towercooler.com
>
>
> -----Original Message-----
> From: Vanagon Mailing List [mailto:vanagon@GERRY.VANAGON.COM] On Behalf Of
> John Rodgers
> Sent: Saturday, April 24, 2010 12:39 PM
> To: vanagon@GERRY.VANAGON.COM
> Subject: Re: alternator installation
>
> It's been a long time since I have thought on this - but I seem to recall
> that a strong charge from the battery(or jumper battery) is required to
> activate the field of the Alternator or the thing won't charge, even if it
> is turning. If your battery is strong enough to turn your starter motor -
> which takes a whopping amount of amps to turn against the load of the engine
> - it should be charged sufficiently to activate the field.
>
> John Rodgers
> Clayartist and Moldmaker
> 88'GL VW Bus Driver
> Chelsea, AL
> Http://www.moldhaus.com
>
>
> On 4/24/2010 11:41 AM, Bill MacLachlan wrote:
>
>> Hi all
>> List wisdom&   experience needed:
>> I'm installing a new alternator.
>> Label on the new alternator says have the battery fully charged before
>> hooking up the alternator.
>> My battery is low.
>> How critical is the warning?
>> Do I have to dig out the trickle charger and recharge the battery first?
>>
>> thanks
>>
>> Bill M
>> 82 GL I4
>>
>>
>>
>>
>
>