Put in new switches. When open there should be no current ie no ohms/open,
when closed should be only 1 or 2 ohms. Test release pressure with rubber
tipped air nozzel and regulated air pressure valve with VOM attached.
Always verify function, whether used or new. Make certain you have not
confuzed a temp sensor with the pressure switch as they look much the same.
If a new longblock does not come with new, tested oil pressure switch(s),
look for a better vendor. A sure sign of compromise which can pervade every
process in the rebuilding.

At 02:02 AM 02/15/2000 -0500, you wrote:
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>1991 Volkswagen Vanagon 2.1 L
>
>Trans:         Standard
>Mileage:       200,000 km
>VIN:           WV2ZB0256M
>
>Misc Data:     Synchro
>Affected Item: oil light
>
>___________________________ FIX: ___________________________
>
>Thanks for the 30 or so replies I received. We decided that
>22 psi @ 2000rpm with 20W50 oil was too low, so we returned
>the used engine to its source and installed a VW Canada
>rebuild with the customer's concurrence. The lesson, I
>guess is that when you obtain a used engine from an unknown
>source, don't accept anything that they tell you about it.
>They said they had checked the compression and oil pressure
>on this one, yet both oil pressure switched were buried in
>filth and the spark plug connectors were heat welded to the
>plug insulators!
>
>____________________ ORIGINAL MESSAGE: _____________________
>
>After installing replacement engine, oil light flashes when
>engine is warm and idling. I installed a new grey oil
>pressure sensor in the port below the water pump. This did
>not change anything. I then found out that there is a
>second oil pressure sensor between the push rod tubes on
>the left side of the engine. I replaced that one with a
>known good grey switch. This did not change anything. I
>have not checked the actual pressure because I do not have
>the necessary adapters for my oil pressure gauge, and also
>because of the inaccessibility of the ports. I measured the
>resistance of the switches and found them to be 2.5k with
>the engine off and about 400 with the engine running. Can
>anyone explain to me how this system works? Things were so
>much simpler when VW's used air to cool their engines!
>Thank you in advance.
>
>Richard Meissenheimer
>bonnie_baker@telus.net
>Technician/Shop Foreman
>Lakeside Auto Sales
>Nelson, British Columbia, Canada
>
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T.P. Stephens aka Doktor Tim
San Juan Island, WA