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Date:         Wed, 15 Dec 2010 19:42:03 -0700
Reply-To:     "Michael A. Radtke" <wa7zpu@CISAZ.COM>
Sender:       Vanagon Mailing List <vanagon@gerry.vanagon.com>
From:         "Michael A. Radtke" <wa7zpu@CISAZ.COM>
Subject:      Re: Battery or Charging System Help Please
In-Reply-To:  <4D083A14.4050808@cisaz.com>
Content-Type: text/plain; charset=ISO-8859-1; format=flowed

Mark and David,

Thank you for nagging me.

I did the tests that I should have done in the first place and found that one of the crimps had failed on the parallel wires at the clean and shiny end in the junction box. I rebuilt and soldered all of the crimps. This brought the voltage drop from the alternator to the battery under load to 0.5 volts. That still bothered me so I installed the recommended jumper from the alternator to the starter. The jumper reduced the total drop to about 250 millivolts.

Thank you for not letting me walk away from the real problem.

Mike

-------- Original Message -------- Subject: Re: Battery or Charging System Help Please Date: Tue, 14 Dec 2010 20:46:28 -0700 From: Michael A. Radtke <wa7zpu@cisaz.com> Reply-To: wa7zpu@arrl.net To: vanagon@GERRY.VANAGON.COM References: <4D059188.10603@cisaz.com> <4D07C4EF.3090601@cisaz.com> <4D07D368.4090907@cox.net>

Mark and David,

Thanks for your posts.

Here is the error in my reasoning. I measured the alternator voltage as ~13.8, the voltage at the junction under the cover as ~13.2 and the battery voltage as ~12.6 with the 2 heater blower and headlight load. Because the drops were approximately equal, I concluded that it was very unlikely that there were two similar failures and that this was the expected voltage drop under these conditions. I didn't do the math.

So tonight I got out my reference books and looked at the wire sizes and I agree with David, 200-300 millivolts appears correct.

I will repeat my measurements tomorrow with the new battery. There exists the possibility that the battery was drawing a lot of current. If I see the same one volt drop from the alternator to the battery, I will do the pin technique on the wires and isolate the problem. I also can use a DC clamp on current meter to read the current.

I also agree with Mark that adding the wire as VW did for an improvement in later models would help. However, my Vanagon has been doing just fine for 25 years without the modification so I am not ready to make that addition ... yet.

Thanks again for all of your suggestions. I'll post in a day or two with the results of my testing.

Mike


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