Date:         Thu, 7 Jun 2012 15:05:36 -0700
Reply-To:     Rocket J Squirrel <camping.elliott@GMAIL.COM>
Sender:       Vanagon Mailing List <vanagon@gerry.vanagon.com>
From:         Rocket J Squirrel <camping.elliott@GMAIL.COM>
Subject:      Re: cluster troubleshooting
Comments: To: pickle vanagon <greenvanagon@GMAIL.COM>
In-Reply-To:  <CA+n284P3x8y8BfeGSNLBFfzShEB+t73yK7bhpYgQ6AOqzbAebg@mail.gmail.com>
Content-Type: text/plain; charset=ISO-8859-1; format=flowed

I daresay that if you hooked your battery up backwards that diode would
be vapor in about 10 milliseconds.

--
Jack "Rocket j Squirrel" Elliott
1984 Westfalia, auto trans,
Bend, Ore.

On 06/07/2012 10:43 AM, pickle vanagon wrote:
> It's one of these:
> http://www.radioshack.com/product/index.jsp?productId=2036270
>
> pointed from ground to +12v.
>
> The only explanation I had, was that if you hooked up your battery
> backwards (oops!) and ran power through the cluster backwards, all the
> current would pass through this diode and blow a fuse, and not damage any
> of the gauge circuits.  But I'm not sure if that really would be a design
> goal.
>
>
>
> On Thu, Jun 7, 2012 at 1:30 PM, David Beierl<dbeierl@attglobal.net>  wrote:
>
>> At 12:50 PM 6/7/2012, pickle vanagon wrote:
>>
>>> We made some good progress on this project last night, but there something
>>> that is puzzling me about the foil.  In the bank of resistors on the back
>>> of the foil, the third one down is a diode which goes from ground to
>>> positive 12v.  What is the purpose of this kind of arrangement??
>>>
>>
>> If it's a Zener (symbol would have little wings slanting up and down from
>> the ends of the line) it could be an overvoltage limiter.  Even a plain
>> diode (reverse biased of course) could be to suppress ringing/spikes when
>> the panel is shut down.  If it's forward biased (arrow pointing toward
>> ground) then you haven't traced it correctly.
>>
>> VW had a tech note at some point about adding a diode when replacing the
>> panel voltage regulator, but I don't remember what precisely it connected
>> to.
>>
>> Got a number on it?
>>
>> Yours,
>> David
>>