[Vwdiesel] Oil Pressure Testing on an '84 Bunny

82 Diesel Westy dieselwesty at yahoo.com
Tue Nov 28 12:57:02 EST 2006

Bryan, GREAT great explaination and will snip for my
files as well.
I have 92 Eco Diesel and was wondering why I have a
white wire with red strip connected to the W term of
my alt. when I have no tach. in the dash?

I bet that is going to the relay as you have stated.  

Thanks a bunch.

Bryan from NJ

--- 'Bryan K Walton' <bryankwalton at machlink.com>

> I thought I'd send a followup to the list regarding
> my fix to my
> oil pressure warning problem on my '84 Bunny in case
> anybody else ever
> has a similar problem.
> To bring everybody up to speed, my problem was that
> my oil pressure
> warning light would come on while idling with the
> oil up to temperature.
> I checked the pressure with a gauge and new that my
> pressure was good.
> Through a process of elimination (following the
> Bentley instructions),
> I also new that the sender on the cylinder head was
> good (this is the
> sender that normally governs the warning light
> during idle).
> Here is what I discovered.  The high pressure sender
> on the oil filter
> flange is designed to trip when the pressure is
> between 23 and 29psi. 
> What Bentley doesn't make very clear is that it
> trips in this range
> REGARDLESS of the rpms.  In other words, if the
> pressure is 28psi at
> the oil filter when idling with warmed up oil, it is
> going to trip --
> even though you are idling.  It is the job of the
> oil pressure relay
> to determine whether the car is above 2000 rpms or
> not when it receives
> this signal from the high pressure sender.
> My problem was with the relay.  Essentially it was
> stuck open.  It was
> never reading the rpms from the tach.  So, at hot
> idle, when pressure
> is lowest, my oil pressure was just low enough to
> trip the high 
> pressure signal (right under 29psi) and by fault, my
> relay was
> allowing the current to flow to the warning light --
> rather than
> blocking that signal like it is designed to do.
> In hindsight, had I understood this design as well
> as I do now, the
> fact that the relay's buzzer never sounded would
> have hinted at 
> the relay as being suspect. I replaced the relay and
> now my light no 
> longer comes on while driving. (And when testing,
> everything now works
> at it should have -- including the warning buzzer).
> Cheers,
> Bryan
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