Thanks for all the replies, guys.

I don't know the idle speed as I don't have a tach.  This episode has got
me convinced that I should remedy that.  I can hook something up to check
the rpms from the engine bay but that's not really going to be that useful
I think, since I suspect that what's going on is that I have an occasional
low rpm issue that arises in certain conditions.  I actually already a wire
I ran coil to the dash a while back, I just haven't hooked it up to
anything yet.  Is the best tach the one in a cluster from a later year
vanagon?

Oil is not overfilled.   I strive for the halfway mark, though right now
its 3/4's of the way up.

The engine hasn't been rebuilt (although I did the top end a few years ago).

I guess my only other question at this point is whether a VDO gauge setup
is accurate enough for the purpose of checking the running oil pressure?

On Mon, Nov 28, 2011 at 7:58 AM, Dennis Haynes <d23haynes57@hotmail.com>wrote:

> What speed is the engine idling at? Much below 850 will cause the light to
> flicker. I set to 900-950.
> Oil level? Be sure it is not overfilled. The top mark is not the full mark,
> it is the "Max do not exceed no matter what" mark.
> The Mobil 15w-50 is good down to near single digits. The Castrol 5w-50
> seems
> to thin out at higher temps even though it should be the same viscosity as
> 50 at 100C.
> Is this an original engine with 100K on it or a rebuild? The 1.9L do wear
> the bearing saddles and loos oil pressure over time. The owner's manual
> even
> states that in some conditions the warning light will come on. It would be
> good to test the oil pressure. The wear limit is 28 psi at 4,000 rpm.
>
> Dennis
>
> -----Original Message-----
> From: Vanagon Mailing List [mailto:vanagon@gerry.vanagon.com] On Behalf Of
> pickle vanagon
> Sent: Sunday, November 27, 2011 10:27 PM
> To: vanagon@GERRY.VANAGON.COM
> Subject: Oil pressure light in 1.9l at idle
>
> On our returning-home-after-thanksgiving drive, we had some scary oil light
> flicker.
>
> Here are the details:
>
> Engine has just a little over 100k miles on it.
> I typically run Mobil 1 15w50 in it, but shortly before this drive changed
> the oil to Castrol Syntec 5w50, hoping to achieve better lubrication during
> cold-starts in the winter.  I used a Mobil 1 filter (which I've used
> occasionally before, though now it was replacing a Fram tough-guard).
> Flicker definitely seemed related to oil pressure.  That is: it only came
> on
> after driving fast for a long block of time, and then letting the engine
> drop to idle.  After I first noticed a flicker happen once and confirming
> the oil level was fine, I tried this experiment several times and could
> often get some flickers out of it, although not always.  Raising the engine
> rpms *at all* would completely kill the flicker.  I couldn't give it even a
> tiny amount of gas and still have flicker, even after a long run.
>
> Further mitigating factors:
> We have an auxiliary battery setup with heavy gauge wire coupling the
> batteries via a Stancor relay.  The auxiliary battery is a year old or so
> and so almost certainly in worse condition than the starter battery, since
> that never gets drained at all.  I have the batteries set up so that a
> switch can be used to kill the stancor relay when driving (or force it to
> be
> engaged when the engine is off).  Anyways, with the stancor relay disabled,
> I wouldn't get any oil light flicker, as the engine was idling high enough
> to avoid it.  The flicker was only happening after a long fast run *and* at
> especially low rpms, which would only happen when both batteries where
> being
> powered by the alternator.
>
>
> Obviously I find this all pretty scary!  I figure the first step is to
> figure out what my oil pressure is at various operating speeds and
> temperatures.  So I've ordered parts to install an oil pressure gauge.
>
> I realize there's a lower threshold (blue) .25 bar switch that VW
> recommends
> to replace the existing .3 bar switch, which would likely eliminate my
> flicker,  but right now I'm just worried this is an indication of deeper
> problems.  I've ordered one of these switches anyways just in case my
> current switch is bad, but the behavior I'm seeing rules out a wiring issue
> I think, and I haven't actually heard of anyone having an old switch that
> was still responding, but just at too high a pressure (if anything I would
> expect them to fail in the other direction.)
>
> I also realize the switch to castrol 5w50 may have been what made the
> difference.  But I'm reluctant to throw back in some 15w50, have the light
> go back off, and then just call the problem solved... I mean, I shouldn't
> really be that close to the edge of triggering the switch right?  Or should
> I be considering it likely that the 5w50 really was just too unstable in a
> 1.9l (which has no oil cooler) at high speeds?
>
>
> I'll be grateful for any advice... wow, I hope this engine isn't giving up
> on us!!  I was planning on getting a lot more life out of it...
>
>