you got it exactly .
it's either directly off 'main bus voltage that's switched' .

and the idea of a relay doesn't sound that right. 
  ----- Original Message ----- 
  From: Ry 
  To: Scott Daniel - Turbovans 
  Cc: vanagon@gerry.vanagon.com 
  Sent: Friday, July 23, 2010 7:37 PM
  Subject: Re: Broken Oil Pressure gauge/sender?

  Scott,
  I'm not positive.... that's the best place to be measuring voltage.  I would like it to come direct from (+) on the battery too, but I wanted it switched.   Not sure how to easily do that without some relay... O_o

  peace,
  -Ry
  http://www.google.com/profiles/rylincoln

  On Fri, Jul 23, 2010 at 8:45 PM, Scott Daniel - Turbovans <scottdaniel@turbovans.com> wrote:

    I would start at the back of the oil pressure gauge.
    it's 3 wires, right ?
    12 volts, usually 'key on' ..
    signal from sender.
    and ground.

    check each of those.
    if the wire from the sender is grounded anywhere ..
    that will make the gauge to go maxed out reading.

    hopefully the sender isn't shorted out or damaged somehow.  or gouge for that matter.

    are you sure the yellow/black wire it a correct one to read charging voltage on ?
    I would want to read it directly from battery positive, or the equivalent. ..
    though you want it switched of course.

    Scott
    ----- Original Message ----- From: "Ry" <rylincoln@GMAIL.COM>
    To: <vanagon@GERRY.VANAGON.COM>
    Sent: Friday, July 23, 2010 6:23 PM
    Subject: Broken Oil Pressure gauge/sender?

      I was wiring up my new VDO volt gauge and accidentally shorted the (+) feed
      to my oil pressure gauge(popping a fuse)

      I finished the job and popped a new fuse in.  Volt gauge works fine, getting
      ~ 13.8 volts.  This is tapped into yellow/black wire coming from ignition
      switch.

      All gauges have grounds going to one of the grounding rings behind and above
      the fuse block.

      The problem is my oil pressure gauges just pegs out max now.  I'm not sure
      how to trouble shoot if it's sender or gauge.

      NOTE* Oil pressure gauge was working perfectly fine BEFORE i wired up that
      volt gauge.

      I disconnected every wire going to the volt gauge and the Oil pressure gauge
      does the exact same thing still, pegging out.

      any ideas how to trouble shoot this are welcome! :)  thanks in advance.

      I SHOULD HAVE WORKED WITH THE BATTERY DISCONNECTED! DOH! :(

      -Ry
      http://www.google.com/profiles/rylincoln