Follow Bentley's procedure, replace sender if in doubt.  
 

> Date: Sat, 3 Sep 2011 20:55:44 -0400
> From: phishman068@GMAIL.COM
> Subject: 2.1 Oil light on at low speeds
> To: vanagon@GERRY.VANAGON.COM
> 
> On my project syncro (which has sat for a long time) I am now finding that
> the oil light comes on and off at Idle once the engine is fully warmed up.
> What's the best proceedure for diagnosing this problem?
> 
> It's running fresh 15W40 oil and a fresh filter.
> 
> -Craig