Date: Wed, 21 May 2003 23:02:43 -0400
Reply-To: Dennis Haynes <dhaynes@OPTONLINE.NET>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: Dennis Haynes <dhaynes@OPTONLINE.NET>
Subject: Re: Oil Light / Buzzer despite NORMAL pressure
In-Reply-To: <PJEPLNDNOHJGHAAMFCMEKECFCGAA.bbeasley@mix.wvu.edu>
Content-type: text/plain; charset=us-ascii
There is lots of info in the archives. Cutting the wires makes things
worse.
The dynamic oil pressure warning system is designed to be fail safe.
There are basically two circuits.
The low speed-pressure system consists of a low pressure switch sensing
oil pressure at the lowest pressure point in the system, the center cam
bearing. The switch is a .3 bar switch the normally closed (in your
hand) that opens when there is sufficient pressure. At low engine
speeds, this switch being closed will cause the oil pressure warning
light to turn on or flash, depending on year.
The higher speed-pressure system consists of .9 bar switch, located
close to the oil pump discharge. It is before the oil filter and oil
pressure relief valve. This switch is normally open, (in your hand) and
closes when there is sufficient oil pressure for it to activate. The
control board looks at this switch when the engine speed is ~2,200 rpm
and above. If this switch does not close at speed, the warning light
will flash and the buzzer will sound. This is an attempt to get your
attention as insufficient oil pressure will quickly result in engine
damage when under load. This feature was added as only having the low
pressure warning system was useless, particularly on the inline 4
engines which do not have cam bearings. Loss of oil pressure results in
a trashed head very quickly. At speed, the low pressure warning does
nothing more than let you know your engine is gone. Take the time to
properly fix the warning system or get a gauge set up.
Dennis
-----Original Message-----
From: Vanagon Mailing List [mailto:vanagon@GERRY.VANAGON.COM] On Behalf
Of Benjamin E. Beasley
Sent: Wednesday, May 21, 2003 3:08 PM
To: vanagon@GERRY.VANAGON.COM
Subject: Oil Light / Buzzer despite NORMAL pressure
I'm really hoping y'all can assist me with this one,
Last winter, my '87 Synro had the nasty habit of flashing the oil light
/
buzzer when the tach hit about 2200 rpm and the engine was cold. No
problem, I would just let the engine warm up a little and then go with
no
subsequent arousal of the oil light. Just to be thorough, I replaced
the
rear oil pressure switch, the one behind the belts and all of a sudden,
the
oil light / buzzer came on immediately after starting the car and stayed
on.
This happened in the middle of my recent trip to Arizona so I rigged a
test
light to that rear oil pressure switch (light on when key on, goes out
when
engine cranks) and hung it from the A/C condenser housing so I could see
it
in the rear view. Then I destroyed the little clapper in the instrument
panel that allows the light/buzzer to do it's thing. Now, the system
was
almost perfect but failed to account for the front oil pressure switch
(plus, was afraid it would come on during daytime and I wouldn't pick up
on
it) so I replaced the entire instrument panel with a better used one
(odometer wasn't working either). After hooking everything up EXCEPT
the
oil pressure wiring in the engine bay, the light/buzzer come on right
after
starting the vanagon. My question is, with no signal coming forward
from
the engine bay does the circuit know that something is awry and sound
the
alarm? Should I disconnect my test light and go through the acrobatics
of
reconnecting the rear oil pressure switch (mirror on a stick and 90
degree
pliers)? Or does this mean that my new oil pressure switch is faulty as
well? Any thoughts of other stuff to check? I should mention that I've
tested the front oil pressure switch and it is not to blame.
Ben Beasley
1987 Syncro Vanagon GL "Babe, the Big Blue Ox"
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