Date:         Wed, 13 Mar 2002 15:42:46 -0500
Reply-To:     Ben huot <huotx@VIDEOTRON.CA>
Sender:       Vanagon Mailing List <vanagon@gerry.vanagon.com>
From:         Ben huot <huotx@VIDEOTRON.CA>
Subject:      Oil pressure sander/switch anatomy. (explanation)
Content-Type: text/plain; charset=ISO-8859-1

First let me thank everybody on this list, you're all very nice and
helpful.
This list helps save a lot of money, time and trouble (and keep the VW
spirit alive). So I wish to help a few if I can.
Here is my 2 cent for now.
I am a Webmaster and with time I will put a lot of information online, if
you have picture or test you would like to put on line, I would host them
and put you name beside. This is just for the love of Westy.
My page: http://pages.infinit.net/eurokit/

An older post I did I wile ago on http://www.westfalia.org
If you still wonder about the oil pressure sender / switch idiot light
problem

Good day (1987 Westy 2.1 / 148000km), I had the "Oil light / flicker"
problem this weekend at idle (800-900rpm) with engine hot and after a 150mi
trip. Oil is10w40 and VW original black oil filter (very hot weather 90F).
This problem did occur only 2 time (1 stop for gas and final destination)
and only one day, on my way back I had no problem!!! (higher temperature /
94F), so we (my friend as a garage) did a Oil pressure test this morning
per Bentley and everything seem fine (about 8/12psi at idle and 45/60psi at
200 rpm /engine warm/hot). The question is how low can you go!!!, I did a
bit of research this morning and came up with the following post… (it
doesn't give me the answer I am looking for but it is a good simple
explanation of how the Westfalia engine oil light system works, now I know
why it is call the "Idiot light")

The following is a good post I found on another site:

Note from me (Ben): the .3 bar oil pressure switch located between the 2
left cylinder pushrod should be change if your not sure about her history,
I almost blown a engine because of that switch. (see my post under:
engine>Oil Pressure switches & release valves)

Why does the light go out at 2000 RPM?

While there is a "high" pressure switch and a "low" pressure switch, they
both cause warnings when the oil pressure drops too LOW. Since "too low" is
a bit of a subjective thing in an engine, VW decided to implement two
standards. The higher the engine RPM, the higher the oil pressure should
be. If you have just one oil pressure switch with a set point low enough
(say 4.4PSI, 0.3 bar) to not engage at idle, that leaves way too much slack
for when the engine is at high RPMs when the engine should have at least
13.2 PSI (0.9 bar) . The "low" pressure switch is used to alert the driver
if the oils pressure dips too LOW while the engine is running at less than
2000 RPM and the "high" pressure switch is used to alert the driver if the
oils pressure dips too LOW while the engine is running at more than 2000
RPM.

More specifically it works like this:
The dynamic oil pressure monitoring system gets inputs from two pressure
switches. One switch is closed with no oil pressure and opens when oil
pressure rises to about 0.3 bar, called the .3 bar switch. The .3 bar
switch is located between the left (driver's side) two cylinders
(pushrods). The other switch is open with no oil pressure and closes when
oil pressure rises to about 0.9 bar, thus called the .9 bar switch. The .9
bar switch is located below the water pump & crank pulley, near the oil
pump.
(I just found this one location today with the help of William Polowniak
photo's  & other good member of the list)

The monitoring system seems to only "look at" the .3 bar switch below 2000
RPM and ignore the .9 bar switch. Above 2000 RPM the active switch is the
.9 bar switch while the .3 bar switch is ignored. Below I've described a
properly operating monitoring system. Note that I say "monitoring system"
because some of the conditions describe an abnormally low oil pressure
condition.

A. Ignition ON, engine NOT running -- or -- engine running at LESS than
2000RPM

(.9 bar switch is ignored)

1. Low oil pressure exists (below .3 bar), keeping .3 bar switch closed
----Oil light: Flashes
----Buzzer: Silent

2. Normal oil pressure exists (above .3 bar), opening .3 bar switch
----Oil light: Off
----Buzzer: Silent

B. Engine running at MORE than 2000RPM

(.3 bar switch is ignored)

1. Low oil pressure exists (below .9 bar), keeping .9 bar switch open
----Oil light: Flashes
----Buzzer: Sounds

2. Normal oil pressure exists (above .9 bar), closing .9 bar switch
----Oil light: Off
----Buzzer: Silent

Also from another post but in regard of the same topic:

Just so you know! (87 Westy-138k), between the 2 left cylinder, there is a
oil pressure switch (hidden by the protective metal shield "and rusted to
the bone"), mine was leaking bad!!!, I have lost more than half of the oil
(in a 10 minute drive). The switch give no warning at all as she still had
pressure!!!. I was lucky (it could have been a blown engine) that I work
close to my home. (Major spill in my garage)
Be aware that this is a very serious problem, (oil is a must) and this part
should be CHANGE before any major trip. It is a easy job to do, it take a
24mm socket head and an hour to change. I did only 400k(186mi)(just bought
it) and I did a head-gasket change, add 2 tows, oil leak and a major
electrical problem, I don't blame the van but the very bad "PO"
maintenance. I have bought a lemon and I have now 2 choices, sell the van
or get the best out of it.
(I was mad at the time (last years), does it show!!!!!!!)

Regards, Ben

ps.: sorry for my poor english, i'm french speaking (italian and spanish
also)