Oil light goes out before start up.

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I got an '86 Vanagon with a diesel swap. The oil light used to light up before starting and stay lit till started.
Now it goes out before starting.

I checked to see if the oil light would light up when grounding both wires and engine running, no light or buzzer.

Know I do have to say that I was just in the speedo cluster to fix the Odometer, but what might of happened?

Any ideas?

[bajacalal]

IIRC the way it works is as follows:

There is a low pressure sender that opens the circuit when there is oil pressure, that is on the head. There is a high pressure sender (something like 20 PSI) that closes the circuit (to ground) when there is sufficient oil pressure above a certain RPM (2000 I think).

IMO the whole "dynamic oil pressure monitoring" or however VW calls this thing is stupid, problematic and a poor substitute for an oil pressure gauge. I have problems with mine operating erratically, in my case it's caused by poor connections at the plug on the instrument cluster. My temporary solution was to remove the instrument cluster bezel so I can stick my hand in there and push on the plug when it starts to do this.

[8v-of-fury]

Colud have maybe knocked a solder joint loose s well eh?

Sorry for the granarical errors... New iPhone lol and big thumbs

[Vincent Waldon]

Now it goes out before starting.

Just to be really clear... does it go out *while* you are cranking, or does it go out all by itself if you just leave the key in the "on" position *without* cranking?

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The light would come on and the off, like a flash. 
Now if by some strange auto-fix, now all is working right  .
Also I knoticed that the dash lights started to work to.

So I know I left something loose. But have you ever seen a good Vanagon instrument cluster that doesn't have all the tabs crusted off.
So that will need to be fixed.
Thanks for your replies.

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Ok. So I took apart the cluster and found that one of the little copper fingers of the trace on the end where the connector fits, had peeled up and rooled back. Not making the right connection.
So I gently unrolled it w/ small paper clip and reinstalled the connector  .
Now it functions better than before. 

I got lucky not having to diag. oil control BS.