Look for the wiring that grounds the instrument cluster to be bad.
 "Slowly illuminates"  Is not an engine problem, but an electrical
voltage problem.  Ether thru a bad ground, or the voltage stabilizer.
                                                      Eric

vwelkers wrote:

>Hello to all-
>
>I used to be on the list years ago and have recently been added in digest
>mode...  I'm stumped with a oil pressure light problem so I'm looking for
>help!
>
>The oil pressure light in my 1987 Vanagon blinks as expected when turning
>the key before starting the engine, then is "off" after starting the van,
>then after approx. 2 seconds, slowly illuminates and stays "on".
>
>It's a rebuilt engine with approx 4000 miles.  New senders were installed on
>rebuild (0.3 bar and 0.9 bar).  I use 20W-50 oil and Mahn oil filter.
>
>I removed the 0.3 bar sender and measured oil pressure.  It is 45 PSI at
>idle and drops to 15 PSI after engine warms up (temp needle in middle of
>guage).  Goes to 20-25 PSI when engine is 2000+ RPM.
>
>0.9 bar sender measures open to chassis gnd when engine not running and
>under 60 ohms after starting engine.
>
>0.3 bar sender measures 10 ohms to chassis gnd when engine not running and
>open when engine running.
>
>I've even tried a different instrument cluster assy to test the dynamic oil
>pressure control board and it does the same thing.
>
>Any help appreciated!  Please reply to vwelkers@highstream.net since I am in
>digest mode.
>
>Thanks-
>
>Vic Welker
>Santa Ynez, CA
>87 vanagon GL Wolfsburg
>93 Passat GLX
>94 Jetta GL
>
>
>
>