Date:         Tue, 23 Mar 2010 22:17:07 -0400
Reply-To:     David Beierl <dbeierl@ATTGLOBAL.NET>
Sender:       Vanagon Mailing List <vanagon@gerry.vanagon.com>
From:         David Beierl <dbeierl@ATTGLOBAL.NET>
Subject:      Re: Cranks but now, STARTS!
Comments: To: Gerald Masar <azsun99@EARTHLINK.NET>
In-Reply-To:  <A374DD45091F478C9818267794C1EEB4@emachine7af6b9>
Content-Type: text/plain; charset="us-ascii"; format=flowed

Dear Jerry,

At 08:26 PM 3/23/2010, Gerald Masar wrote:
>The diagram on the VW relay has 87A connected to the same line as
>86, but with a symbol that looks like a diode.

Because it is a diode. :-)  Looking on 97.206, current tracks 36 and
37, let's see if we can figure it out:

a) At the relay terminals:
Both terminals 4/86 and 5/15 will actuate the relay if they receive
+12v.  If it's 86 that gets the voltage that's all that will
happen.   The other terminal will not have voltage on it.  OTOH if
it's 5/15/87A that is energized, two things will happen.  The coil
will actuate and there will also be 12 v on terminal 86, driving some
device(s) back up the wiring somewhere.

b) In the larger circuit:
Relay terminal 86 is driven from pin 23 of the ECU at track 23
(coincidence).  It connects to nothing else; so when pin 23 goes
active the ECU relay actuates but nothing else happens.

Relay terminal 5/15/87A is connected to the + terminal of the
ignition coil and various other places and that whole two-relay + ECU
circuit makes my head spin.

So I'll just say that VW put that diode in there intentionally, and
if it's left out *something* in the ECU/fuel system is going to work
differently than before, and in that sense it's broken.  There also
may be loss of the magic smoke from some component(s), so all in all
I'd stick with the diode until the day may come when you know exactly
what effects that change would make.  If I happen to figure it out
I'll let you know. <g>

Yours,
David