The black line is the vacuum source and the white-Blue goes to the actuator.
That is not a switch but a valve. Under the van there is a vacuum reservoir
that almost looks like 3 balls. There is a tee and a check valve off the
brake booster vacuum line. The valve or tee sometimes gets clogged. Note
that all this tubing and that restrictive check valve limits the flow
available. If the actuator fails (common), the system will lose vacuum quick
and you will need to cap things off and do some testing allowing some time
for the reservoir to fill. Get a vacuum gauge and a pump to test each part
of the system.

Dennis

-----Original Message-----
From: Vanagon Mailing List [mailto:vanagon@gerry.vanagon.com] On Behalf Of
Jon Kanas
Sent: Saturday, December 10, 2011 7:12 PM
To: vanagon@GERRY.VANAGON.COM
Subject: No vacuum @ locking diff control

  Greetings folks,

I discovered awhile back that the locking differential wouldn't engage, and
the dash switch didn't hiss like it normally does.  I pulled the switch, and
checked for vacuum on all three lines (white, black, blue).

    Where is the source of the vacuum for the locking
    differential switch?
    Which of the three lines should have vacuum at the switch?
    Any suggestion where I should start looking for a broken
    or disconnected line?

It's cold and wet out here in Colorado, so I'd like to minimize the search.
--

*Thanks and Happy Holidays,
Jon B Kanas
Email: kanas@qadas.com <mailto:kanas@qadas.com> Longmont, Colorado; Cultural
Center of the Universe
Website: http://www.qadas.com/~kanas
<http://www.qadas.com/%7Ekanas> *