I don't claim to be an AC expert, but I have never heard of such a
switch and have not encountered one in the 4 or 5 systems that I have
worked on.

I believe that in the original Vanagon diesels the solution was simply
to not put AC in the diesels.  ;-)  Too little HP.
   In the 2.1 L Vanagons the idle speed controller and the ECU give it a
little more gas when the AC is on.  If your AC turned off at idle, it
wouldn't be worth much when stuck in traffic jams in the summer.
    Perhaps someone else can tell us what the approach is in the new
generation of VW diesels.

Larry A.

Matthew wrote:
> I am helping a friend convert a gas-powered land
> crusing to a diesel powered land crusier. check out
> this link for his details, insane what he has done:
> http://forum.ih8mud.com/index.php?board=21;action=display;threadid=13204
>
> Anyways, the old (gas engine) ac system has a switch
> that is triggered by a pulse coming off the
> distributor, so it knows at what rpms to shut off the
> AC compressor. Diesels don't have a distributor...
>
> So, on vw diesel engines, what controls the compressor
> clutch? Is there an automatic switch that will turn on
> and off the magnetic ac compressor clutch when the
> engine rpms are too low? How does the vw diesel setup
> work for ac?
>
> thanks
> matthew
>
> =====
> Matthew Pollard         "Racing with the wind and flirting with death
> Dept. Of Chemistry     So have a cup of coffee and catch your breath"
> University of Idaho
> www.ftir.chem.uidaho.edu
>
>
>
>
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