Date:         Mon, 30 Jul 2001 00:13:04 +1000
Reply-To:     Chris Mundy <cwmundy@OPTUSNET.COM.AU>
Sender:       Vanagon Mailing List <vanagon@gerry.vanagon.com>
From:         Chris Mundy <cwmundy@OPTUSNET.COM.AU>
Subject:      Dynamic Oil Pressure Sensor behind Speedo, how do they work,
              wiring diagrams, tachometer changes, etc
Comments: To: VW Caravelle AUSNZ Group <caravelleausnz@yahoogroups.com>
Comments: cc: dbeierl@attglobal.net
Content-Type: text/plain; charset="iso-8859-1"

Hi Folks,

Advice required.

I am currently converting my instrument cluster from a standard 89
model(large clock)to an 84 cluster with a tacho.

On the surface the way ahead is to put the 89 Speedo into the 84 Cluster
with Tachometer.

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.

On the 84 Instrument Cluster there is no such thing as the Dynamic Oil
Pressure Sensor however, the printed circuit does allow for one. The basic
operation means that the 0.3 bar plug on the cluster runs through a resistor
to the Oil Pressure LED.

I have managed to map out both circuits and have found that there is only a
small modification required to the 84 circuit and they are

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

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?
2. Has anyone done this before or am I the Lone Ranger, eg 89->84?
3. Is there a circuit diagram in a late model Bentley's on Instrument
Clusters?
4. Has anyone ever purchased or installed the lugs that attach to the wiring
circuit?

By the way, the Instruments all work OK, I've mounted the 89 Speedo in the
84 Cluster, everything works OK, except the Oil Pressure LED doesn't flash
at start up, it just glows then turns off when pressure is recognised just
like your typical design.

This week I will be spending my spare time at the local Electronic Stores
looking for plugs and lug attachments to circuit boards.

TIA



Chris Mundy
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Christopher W. Mundy
Hh: 61 2 62419343 AEST
Wk: 61 2 62446749 AEST
MB: 61 412239144 AEST
E-Mail: cwmundy@optusnet.com.au
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~