Date: Sun, 12 Dec 2010 22:53:55 -0500
Reply-To: David Beierl <dbeierl@ATTGLOBAL.NET>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: David Beierl <dbeierl@ATTGLOBAL.NET>
Subject: Re: Battery or Charging System Help Please
In-Reply-To: <4D059188.10603@cisaz.com>
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At 10:22 PM 12/12/2010, Michael A. Radtke wrote:
>So, I looked at the charging system and was reminded again that the
>Vanagon uses an alternator that supplies a constant voltage at its
>terminals instead of supplying a constant voltage at the battery. With
>the engine at 1000 rpm, I measure 13.8 volts at the alternator with the
>lights and heater blowers turned on, but only 12.6 at the battery. That
>is not enough to maintain the battery.
Try 2,000 rpm, see if there's a difference. 13.8 is a float voltage,
sufficient to maintain existing charge but not enough to add much charge.
>It is most likely that there is a high resistance path in the wiring
>between the alternator and the battery.
And you need to find out where it is. For that you will want your
voltmeter, set on 200 mV or 2 V scale. More below.
> Bentley shows two parallel
>wires from the alternator that connect to a bus wire that runs from the
>heavy starter cable to the front of the Vanagon. I don't know why VW
>didn't run those parallel wires directly to the starter cable.
They needed some power to run the engine harness and decided to get
it from there. You'll be overjoyed to know that at least by '89 they
run a skinny wire for that purpose and a big fat one right to the starter.
> I
>suspect the junction of the parallel alternator wires and the bus wire
>is bad, but I can't locate the connection. Can anyone tell me exactly
>where it is?
Actually Bentley tells you where it is - if you look at the
connection on 97.56 track 22, you'll see a circled 21 beside
it. Go back to 97.54 and look at the list of circled terminal
numbers. #21 is "plus connection, in connector housing" which is the
little wiring box on the forward engine room wall.
>Of course, any other advice on how to trouble shoot the problem would be
>appreciated as well.
Look at all the connections for signs of heat. Heat means that
there's a high resistance there, or was at the time that the heat was
generated.
Then start up the beast and take your voltmeter and start measuring
between pairs of connections *and across the actual connections* to
find where your missing voltage is hiding. 1.2 volts drop with a
current of twenty amps (lights+blower is in that range) means you're
dissipating 25 watts or so somewhere; so something should be getting
warm as well as showing a voltage drop.
Yours,
David