I would be very hesitant to use the coil wire to also supply the ECU.  The
coil is an inductive load which is switched on and off.  This tends to
generate voltage spikes which are  harmful or at least annoying to
sensitive electronics on the same circuit.

Larry A.

On Fri, Jan 25, 2013 at 4:13 PM, neil n <musomuso@gmail.com> wrote:

> Viewing images of other vehicle wiring, it seems some use a relay to
> carry power to the coil.
>
> Jetta Motronic 2.9 uses a 0.5mm wire to ECU. Pretty sure it sends + to
> ECU so ECU will "turn on" and energize other engine management items.
> The '81 Vanagon uses a slightly larger wire to the coil.
>
> Thought: use Vanagon coil wire for  +  to ECU and relay for  +  to the
> Jetta coil
>
> mocked up diagram:
>
>
> https://lh5.googleusercontent.com/-qjVqWgmKgiA/UQLzz0KnCHI/AAAAAAAAGq8/dV79PgDqWQg/s720/ABA%2520swap%2520coil%2520wire%253F.jpg
>
> If I did this, I *think* that when key turned to ign. off,  + to ECU
> will be cut off so engine should shut off regardless if a little +
> power wants to loop back to 15 via the instrument cluster.
>
> Input welcome!
>
> Neil.
>
> On Thu, Jan 24, 2013 at 9:10 PM, neil n <musomuso@gmail.com> wrote:
>
> > .....  it was
> > determined that power from the alternator blue wire was looping back
> > into the + side of the relay coil via the 15 wire to the (dash lights?
> > No Bentley in front of me) But here's the kicker:
> >
> > if I pulled the hand brake on, the engine stopped!
> >
> > Seems the addition of the e-brake light drew enough current to allow
> > the relay to open.
> >
> > This was repeatable but usually only happened when the engine was warm.
> >
> > Neil.
> >
> > On Thu, Jan 24, 2013 at 8:43 PM, David Beierl <dbeierl@attglobal.net>
> wrote:
> >> At 11:27 PM 1/24/2013, neil n wrote:
>
> >>> At one point I'd wired in a relay to be triggered by 15 so it would
> >>> carry power to the ECU and coil. But then there were times when the
> >>> engine wouldn't shut down unless the hand brake was engaged.
> >>
> >>
> >> Uh...why?
> >>
> >> d
> >>
> >>
> >
> >
> >
> > --
> > Neil n
> >
> > 65 kb image Myford Ready For Assembly  http://tinyurl.com/64sx4rp
> >
> > '88 Slate Blue Westy to be named.
> >
> > '81 VanaJetta 2.0 "Jaco"  http://tubaneil.googlepages.com/
> >
> > Vanagon VAG Gas I4/VR Swap Google Group:
> >
> >
> http://groups.google.com/group/vanagons-with-vw-inline-4-cylinder-gas-engines
>
>
>
> --
> Neil n
>
> 65 kb image Myford Ready For Assembly  http://tinyurl.com/64sx4rp
>
> '88 Slate Blue Westy to be named.
>
> '81 VanaJetta 2.0 "Jaco"  http://tubaneil.googlepages.com/
>
> Vanagon VAG Gas I4/VR Swap Google Group:
>
>
> http://groups.google.com/group/vanagons-with-vw-inline-4-cylinder-gas-engines
>