Neil
The diagram is quite legible and confirms that we've correctly identified
the connections to the ICU.  Thank you!

Brett

On Thu, Nov 14, 2013 at 9:30 AM, Neil N <musomuso@gmail.com> wrote:

> Hi Brett et al involved.
>
> Thanks for posting what you're finding. At best I know little about
> all this but know enough to appreciate some of whats involved. I find
> this an interesting thread.
>
> An image from my Digifant pro training manual showing labelled pin
> outs of ISV control unit:
>
>
> https://lh5.googleusercontent.com/-QxW65MiNQlI/UoUHgd3ioUI/AAAAAAAAIp0/rfGr1KsYiho/s512/ISV%2520diagram%25201.jpg
>
> Hope that link works and diagram is legible. I can p-mail a higher
> quality image if you want.
>
> Neil.
>
>
>
> On 11/14/13, Brett Ne <brettn777@gmail.com> wrote:
>
>
> > David Beierl sent me a picture of an oscilloscope tracing from the coil
> > primary circuit during firing and boy, is it ever anti-friendly to
> > microcontrollers!  There's a decent spike up around 30 volts and a very
> > brief spike of over 200 volts!  Fortunately, we don't have to worry about
> > that.  Initially I assumed that since the tachometer in the instrument
> > cluster is driven by the coil primary signal, that the tach info to the
> ICU
> > would have the same source, but it turns out that it gets tach info from
> a
> > common connection (with the ECU) to the output of the Hall sensor.  The
> > Hall sensor won't be above 12 volts(keep in mind that in a car, 12V could
> > really be anywhere between 9-16V).
> >
> > So, I've spent some time looking through Bentley and looking at some
> other
> > sources online to sort through the various connections to the ICU.  Below
> > is a listing of what I've found.  Please look through for any mistakes or
> > misunderstandings.  The terminal numberings are those used in the Bentley
> > wiring diagram for the Digifant 1986 system.
> >
> > ICU(Idle Control Unit) connections:
> > 6/50  Digital input from the starter switch
> >         high when starter is engaged
> >         low when the starter is not engaged
> >
> > 14/15  12V power supply to the ICU whenever the ECU has power
> >            Also supplies power to the power steering pressure switch
> >
> > 15/LH  Digital input from the power steering pressure switch
> >            high when power steering is engaged
> >            low when power steering is not engaged
> >
> > 5/31  Ground connection to the ICU
> >
> > 13/T  Analog input from the coolant temperature sensor
> >
> > 8/LS  Digital input from the throttle valve switch
> >          high when throttle valve closed or wide open (I'm guessing here)
> >          low when thtrottle valve partially open (I'm guessing here)
> >
> > 4/ST2  PWM output to the idle speed stabilizer valve    Note: One of ST1
> > and ST2 is an ground connection and the other will be a
> >
> > PWM power source. Must be tested to see which is ground.
> > 11/ST1  PWM output to the idle speed stabilizer valve
> >
> > 2/K  Digital input from AC compressor
> >        high when AC compressor is on
> >        low when AC compressor is off
> >
> > 17/1  Analog input from the Hall sensor   What is the typical for the
> > baseline voltage and the peak voltage?
>
>
> --
> Neil n
>
> Blog: tubaneil.blogspot.ca
>
> '88 Westy http://tinyurl.com/c8rlw6p
>
> '81 VanaJetta 2.0 "Jaco"  http://tubaneil.googlepages.com/
>
> Vanagon VAG *Gas* inline-VR Engine Swap Group:
>
> http://tinyurl.com/d7gd5ej
>