> I want to know if anyone knows for sure if there is any internal
> differences between the two different Vanagon Air Conditioning compressors
> (SD-508 for 83-85 Vanagons and SD-709 for '86 and newer)?  If they are the
same
> internally then the only real difference is the "head" of the unit (the
back
> end where the lines connect to the compressor) which can be swapped over.

Unfortunately the different units used in the Vanagons (there are actually
three altogether) are not interchangeable.  While Sanden does make a number
of versions of each compressor, with different heads, they still are all
called the same part number.  In other words, two SD709's with different
heads (i.e. one used in a Vanagon versus one used on a Passat) would both
still be called SD709's, but with a different suffix to designate the head
used.  (Incidentally, for that reason, you may also want to take a look at a
508 that your supplier is offering before you sell one, if you haven't
already, just to make sure the one they sell has the correct head for a
Vanagon.)  The 709 is not just a 508 with a different head, it is an
entirely different compressor.  Because there were several different
compressors used, I usually ask my customers to provide me with a detailed
description of how/where the hoses connect to the compressor (or have them
read the complete Sanden number off of their old one) so I can make sure to
send them the correct replacement.  If it's an '83.5-85 Vanagon, you're
pretty safe because they all used SD508's (which I also sell).  But an '86
could use any of three different compressors, and an '87-up one of two. Oh,
and forget the microfiche; I have found it to be less than accurate about
what years used what compressors.  Incidentally, the same holds true with
receiver/dryers; VW used several different ones, and the microfiche does not
accurately identify which Vanagons have which.

- Ron Salmon
  The Bus Depot, Inc.
  http://www.busdepot.com
  (215) 234-VWVW