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Re: [tech] oil pressure switches



Josiah,

The switch on the oil filter flange is for low pressure.  like .03-.5 bar or
whatever it says on the sender.  The sender is supposed to be the white
kinda cone-shaped one.  If this is unplugged the car will idle fine with no
light or buzzer but as soon as you get to 1500 RPMs the buzzer and light
will go off.

The switch on the head which is also cone shaped but brown is for higher
pressure like .5-5 bar or some shit like that.  This switch is not connected
to the buzzer but will cause the light to go on anytime the oil pressure at
the head is less than .5bar

There is a small circuit board on the back of the speedo cluster that
measures input from both of these sources and controls both the light and
the buzzer.  I think this is also somehow tied in to the tach circuit. This
circuit board is what goes bad.  I happen to have two spare boards in a box
if you can figure out which one you need.

Later,

Brian Honnold
'78 Rocco Ragtop (with 84 guage cluster)
-----Original Message-----
From: Wm. Josiah Erikson <josiah@gsinet.net>
To: Scirocco List <scirocco-l@scirocco.org>
Date: Sunday, November 15, 1998 7:02 AM
Subject: [tech] oil pressure switches


>OK, my Bentley is pissing me off. It's contradicting itself again. But
>it's an old one, made in 1983. Maybe the new one doesn't have so many
>mistakes in it... Brian?
>Anyway, I'm dealing with an '84 Scirocco that has the following
>condition: The oil pressure warning light and buzzer stay on for much of
>the time. When the light goes on or off doesn't seem to have much to do
>with anything at all. So I figure I'd see if the oil pressure is good,
>and since I don't have an oil pressure guage, I figured I'd check
>whether the oil pressure switches were setting off the buzzer or whether
>it was something else, and if it was the switches, I'd replace the
>offending one with a used one I had around, and then if the condition
>still existed, conclude that the oil pressure was bad, or at least take
>it somewhere to have it tested.
>So I looked in the trusty Bentley, and it tells me two contradictory
>things:
>1. That the switch on the cylinder head is normally closed and that the
>switch on the oil filter bracket is normally open.
>2. If I disconnect the wire that goes to the switch on the oil filter
>bracket, the warning light should come on and a buzzer sound.
>
>Obviously, these two things are contradictory. If the switch on the oil
>filter bracket is normally open, then disconnecting the wire should make
>the light go out, if anything. So... what's right?
>
>And somebody could tell me what the switch ratings mean, like "a
>normally closed 2.1-6.4 psi switch". Does that mean that it's closed
>between those pressures? Seems odd, because I thought that our engines
>ran up at like 60psi oil pressure.
>
>Anyway, if somebody could enlighten me as to how these switches work,
>I'd be eternally grateful : )
>
>    TIA!
>    -Josiah
>
>
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