> Assuming a properly functioning engine and IS system, if one measured
> current draw at the ISV, loads on and off, at idle, cruising speed and
> WOT, could they get a really good idea of when the ISV is used? (valve
> changes position). Maybe a graphing meter would be useful in this regard?

Current draw or voltage measurements would be kinda okay.  They should be
proportional to the duty cycle, but again, knowing the duty cycle tells you
exactly what the control unit is doing and is much preferred over indirect
measurements.

> My guess is that at idle, no loads (PS, AC) the valve is
> closed. Or.....
>

...or partially open.  We can all guess until we're blue in the face, but
if we want to create a re-engineered control unit that solidly replaces the
old one, we have to establish the behaviors of the old one first

>
> Isn't the ICU basically taken out of the picture any time the throttle
> is just off idle or at WOT?  (throttle enrichment switch activated or
> not).
>

Maybe, maybe not.  Maybe the idle throttle opens fully under full throttle
to help the engine breathe better.  I just don't know.

>
> Did you find the correct "Vanagon" Digifant pro training manual
> online? If not, can send more images. There may be some useful in
> there for your needs.
>

No, I haven't, though to be honest, I haven't been looking.  Typically
training or repair manuals may give enough info to identify a faulty part
but don't give all the details on how that part interacts with all the
other parts of the system.

--
Brett in Portland, OR
"Albert" '82 VanaFox I4 Riviera