Date: Mon, 23 Apr 2001 13:00:22 -0400
Reply-To: David Beierl <dbeierl@attglobal.net>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: David Beierl <dbeierl@attglobal.net>
Subject: Re: Vanagon oil light question for you - dissection of the light
In-Reply-To: <F6hobqcMiRAI5RTHrS000004734@hotmail.com>
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At 11:57 AM 4/23/2001, Brian Cochran wrote:
>compared to the 4 psi of the VW sender. Now, I'm really rambling here, but
>what I think you need to know is the VDO gauge set-up is highly suspect by
>me.
>
>No, then replace the VW oil pre switch first!. Only then, after that fails
>and you are receiving a solid, sickening red light at idle, then go for the
>gauge set up, which spells out, basically, that you are in for some major
>engine repair/replacement. Then go talk to boston bob.
Some other rambling here. <g> When I was in Hospital Corps School, back
when they were starting to put kerosene in lamps instead of whale oil, they
taught me about screening tests vs. diagnostic tests.
Screening tests: 1) are cheap, 2) don't give false negatives, 3) do give
false positives. E.g. the STS (Serological Test for Syphilis).
Diagnostic tests: 1) can be expensive, 2) don't give false positives, 3) do
give false negatives. E.g. the FTA (Fluorescent Treponemal Antibody test,
also for syphilis).
Oil lights and oil gauges are analogous to the extent that lights are cheap
and give good warning of an immediate problem, while gauges are expensive
and give good diagnostic information as to what's going on in the engine vs
what it did last year and last month and last millenium. You can't
diagnose trouble with a light, but it tells you to stop the engine before
you wreck it.
>One final note: if you put in the VDO gauge, do not.....DO NOT use their
>"adapter"/rubber hose 12" extension. First off, it's a $ rip-off. Second,
>I think is a possible reason why I'm still having an INDICATION of low oil
>pressure on a VW rebuid with 70k with one month old rod bearings,heads, oil
>pump,etc. Of course, I'll really know if my engine throws a rod!
Argh! You need to know what your oil pressure is! The VDO is an electric
gauge which is fine if it's working -- but stick in a mechanical gauge as a
test. If it reads the same as the VDO then you can be pretty sure there's
a problem and you can go fix it while it's merely expensive instead of
astronomical. If it reads ok (which I suspect) then you can troubleshoot
the electric gauge at your leisure.
And the other fellow said:
>>My '87 Syncro Westfalia recently began to have its oil
>>warning light come
>>on, at idle or while cruising. I am reluctant to
>>drive at all until I
>>sort it out.
>>This I presume is the 0.3 bar warning coming at idle
>>(<2000 RPM). The
>>glow seems to be voltage dependent: it brightens with
>>higher RPM, and it
>>goes out if one or two electrical items (fan,
>>defroster are turned on).
This is not normal behavior. Bad sender or connections maybe -- but sounds
like bad L-board to me. *If* the L-board gets its supply voltage from the
panel regulator, then could be bad regulator. Also, light is coming on
at >2000 rpm (cruising) but buzzer is not sounding, again not normal behavior.
>>Interestingly, the sender is in full continuity with
>>ground when the
>>engine is off, and not at all in contuity with ground
>>when engine is
>>running. That is, 0 resistance with engine off,
>>infinite resistance with
>>engine on.
Exactly as it should be. Good sender, properly connected.
>>Also interestingly, the dashboard light behaves
>>exactly the same
>>(gradually glows on) when the engine is started and
>>run and the sender
>>wire is DISCONECTED. So I am a little confused.
No, you just haven't put the evidence together. 1) Sender good 2) problem
happens with or without sender connected -- conclusion, it's not the
sender. Actually #2 alone is enough to draw this conclusion.
To make absolutely sure before you start tearing into the L-board, you can
open the panel connector housing and remove the contact for the 0.3 bar
sender. If it gives the same indication (I think it will) then your
problem is within the panel...
David Beierl - Providence, RI
http://pws.prserv.net/synergy/Vanagon/
'84 Westy "Dutiful Passage"
'85 GL "Poor Relation"
