John,
   I am not at home for about a week, so I can't look at the ETKA, but
I am quite certain that there are two service ports; I know there are
on my '91.  I believe that one of them is behind the plastic cover on
the left D pillar.  Follow the hoses!
  It seems to me that there is an error in the Bentley either in an
illustration or the text about which is the high and which is the low
pressure side.  Be careful, the high pressure is always the smaller
diameter hose and the low pressure is the larger one.  You can also go
by where the hoses lead if you are familiar with the overall theory of
the system.

Have fun,
Larry A.

On Wed, Aug 4, 2010 at 11:49 AM, John Rodgers <inua@charter.net> wrote:
> �Volks,
>
> I'm readying to work on the AC system of my '88 GL and have been looking
> at the ETKA Illustrations. The specific illustration is # 41-25.
>
> Can anyone tell me how to 1) enlarge the illustration on the screen, and
> 2) printout the enlarged image?
>
> Also, I note there is seemingly only one service valve on the system
> just a couple of inches behind the compressor. I thought there were
> supposed to be two service valves. Am I missing something here?
>
> I want to upgrade to R134a. Do I need to install two valves, even though
> the original system doesn't seem to have two valves??
>
> Thanks
>
> John
>
> --
> John Rodgers
> Clayartist and Moldmaker
> 88'GL VW Bus Driver
> Chelsea, AL
> Http://www.moldhaus.com
>