Ken Wiliford wrote:

> They only used these SD-510 compressor on some of the '86 and 87
>Vanagons out there.  They were basically a compromise between the older
>compressor SD-508 and the SD-709.  The SD-510 is basically the same as the
>older SD-508 but the "head" is different.  The head is the rear end of the
>compressor where the fittings attach.  The SD-508 has screw on fittings,
>while the SD-510 and the SD-709 have slide in connectors that are held in by
>a bracket with one bolt in the middle.

Actually the first digit in this obsolete Sanden numbering system is the
number of cylinders (i.e. 5 or 7)  and the second and third digits
describe the approximate displacement in cubic inches (i.e. 8, 9, or 10
cu in).  All three compressors can be obtained with a variety of
cylinder head assemblies that have O-ring connections or flair
connections on either the end or on the side of the compressor.  VW
supplied the limited selection Ken mentioned.

If you want to know more about Sanden compressors look at
http://www.sanden.com .  This will keep you busy for hours with the very
interesting technical specs and optimum operating conditions.  It will
also let you identify any Sanden compressor so you have a wider
selection at the junk yard.  It will also identify interchangable parts.

If you have the chance to select between a SD-510 and a SD-709, choose
the SD-709.  It's much smoother and quieter because of more cylinders
and smaller displacement per cylinder.  There is  less tendency for the
compressor to stall and cause the belt to slip when starting.  I have
also been told by an auto air conditioning design company that the
SD-709 is more efficient than the SD-510.

Ed McLean
email99@bellsouth.net