The master place for this is as the msavr wiki:
http://www.squirrelpf.com/msavr/index.php?page=DocsAndFAQ%2FIACFAQ

--- Original anti-confusion material from Dave Brul:
After some confusion over the use of IACs with Pers soft and firmware,
I had a closer look at the three Bosch IAC valves I have on my
workbench, all from scrap.

All three operate differently and there are also discrepancies between
Pers data and those I found when checking against what I got. Here is
my little contribution:

Bosch 0 280 140 505 (Also VW Audi 034 133 455): 
shape: outlet at 90 deg to inlet
total length: 141 mm
Position unpowered: less than 1/4 open, spring centering
Connections:terminals marked 1,2,3 (looking at connector with central
notch on top), when connected as per Pers diagram(1: +12V; 2: grd via
10 ohm; 3: to MS) the valve will be open with 3 open, closed when 3 is
at 12V.
This valve will NOT close when connecting 3 to grd, as it should when
connected to MS Idle out. This is why it will always be open when
hooked to MS. Played with other ways to hook it up, could not find one
which worked


Bosch 0 280 140 501
shape: outlet and inlet in-line
length: 107mm
Position unpowered: indifferent, no spring
Connections: terminals marked 3,4,5 (as above). with +12V connected to
central terminal the valve will be either open or closed with either 3
or 5 conncted to grd.


Bosch 0280 140 516
shape: inlet at 90 deg to outlet, cast body
length: 124 mm

Position unpowered: closed, spring loaded
Connections: two pins. Will open when applying dc, nice linear
response in the range 1 to 9V, 1A at 9V (open)
