Date:         Sat, 26 Mar 2011 17:08:39 -0400
Reply-To:     David Beierl <dbeierl@ATTGLOBAL.NET>
Sender:       Vanagon Mailing List <vanagon@gerry.vanagon.com>
From:         David Beierl <dbeierl@ATTGLOBAL.NET>
Subject:      Re: Alternator question
Comments: To: Greg Potts <greg@POTTSFAMILY.CA>
In-Reply-To:  <4D8E1801.1060103@pottsfamily.ca>
Content-Type: text/plain; charset="us-ascii"; format=flowed

At 12:44 PM 3/26/2011, Greg Potts wrote:
>As Dennis suspected, the battery light does not come on when I first
>turn the key before starting the van. Also possibly related: about a
>week ago I also lost all my dash illumination. The gauges and coolant
>warning light still function however; only the battery indicator and
>dash lights seem to be affected.

The only common point is the fact that both wires go through the
panel connector.


>I have removed and inspected the cluster and everything looks OK; I
>tried swapping the LED's between the OXS and the battery but no luck.

The LED itself actually carries only a minor part of the "tickler"
current that starts the alternator going.  The rest is carried by a
resistor in parallel - it's the large one you can see labeled as R3
on 90.8 fig. 4.  When ALT lights were incandescents that drew a
couple hundred milliamps this wasn't necessary.  But in this case the
LED will carry around 15-20 ma, and the 150 ohm resistor about 80 or so.


>I also checked the connection of the blue wire on the back of the
>alternator and it appears to be clean and well seated.

Pull that wire from the D+ terminal and check the key-on
voltage.  Should be +12 but by the symptoms it will likely be
zero.  If it's zero, follow it back to the panel and find out where
it goes to +12.

If by chance it *is* +12, stick your milliammeter on it and see how
much current it will deliver to ground.  *Ought* to be in the range
of 100 ma (and the light should light), but again I'm not expecting
that it will be.  Ground it or connect it back to the alternator and
again follow it back to see where it turns to +12.*  Can you read the
wiring diagram (97.104 et. seq., tracks 6 and 51) or do you need a
blow-by-blow?

*if it goes to +12 as soon as you hook it back to D+ that indicates
an alternator problem, but that seems unlikely since you've swapped
alternators.

Yrs,
d