Date:         Sun, 29 Jul 2001 14:29:36 -0400
Reply-To:     David Beierl <dbeierl@ATTGLOBAL.NET>
Sender:       Vanagon Mailing List <vanagon@gerry.vanagon.com>
From:         David Beierl <dbeierl@ATTGLOBAL.NET>
Subject:      Re: Dynamic Oil Pressure Sensor behind Speedo, how do they work,
              wiring diagrams, tachometer changes, etc
Comments: To: Chris Mundy <cwmundy@OPTUSNET.COM.AU>
In-Reply-To:  <000c01c11838$f7032c20$64646464@oemcomputer>
Content-Type: text/plain; charset="us-ascii"; format=flowed

At 10:13 AM 7/29/2001, Chris Mundy wrote:

>One of the challenges I have encountered is the fact that the 89 model
>Speedo has the dynamic oil pressure sensor which is designed to flash the
>Oil Pressure LED on low oil pressure and activate the buzzer at "2000" rpm
>when there is no pressure.

[insufficient pressure...]



>remove the resistor,
>attach the dynamic oil pressure switch adaptor (circuit to the Speedo plug)
>to the circuit board.

Yup.  I kind of suspect this is actually an '85 cluster..


>My question to those such as David Beierl who love playing with these things
>are
>
>1. How does the sensor work, is it an IC?

I imagine so -- take a look on the circuit board.

>2. Has anyone done this before or am I the Lone Ranger, eg 89->84?

In the US all the '86 up have tachs, I believe.

>3. Is there a circuit diagram in a late model Bentley's on Instrument
>Clusters?

Not of the innards of the "L-board."  You've already figured out the rest.

>4. Has anyone ever purchased or installed the lugs that attach to the wiring
>circuit?

I doubt it.  Those lugs are stuffed on by a machine that works very
precisely to achieve a "gas-tight" connection that won't corrode.  I
wouldn't mess with them, even if you could find some.

I have heard rumours of people scraping one layer of the plastic off the
circuit foils and soldering to them.  Personally I wouldn't chance it
without a spare, and you wouldn't get a good physical mount anyway.    But
I guess you could solder pigtails on the flex-circuit and run them to a
connector, and you might find by tracing that the end of the circuit
reaching over to the speedometer is expendable (i.e. the rest would still
work even if you cut that section away).  I'm guessing that the actual
connector pins are 0.025" square pins on 0.1" centers -- if so the "Berg
header" connectors to mate are readily available.

The alternative would be splicing wires from the harness to the L-board,
with a plug of some sort in between -- all the signals are available out there.

david


David Beierl - Providence, RI
  http://pws.prserv.net/synergy/Vanagon/
'84 Westy "Dutiful Passage"
'85 GL "Poor Relation"