The oil pressure circuit board was added to the Vanagon with the 1986
model 2.1 engine. Other VW vehicles got it at about the same time. It is
mounted inside the speedo case but has no connection to the speedo
function. The was just where VW decided to put it, it could have been
put almost anywhere.

Oil pressure is created by the oil pump. The oil pump lives inside the
engine and turns faster or slower as the engine turns faster or slower.
The pump make more pressure the faster it turns. The engine needs more
oil pressure when it is under load and turning faster. The original oil
pressure switch only checks for the minimum oil pressure the engine
needs at idle.As soon as this small pressure is reached, the switch is
triggered and the oil light turns off. With the dual switch system of
the 2.1, a second higher pressure switch is also used. This switch is
only hooked up to the warning light when the engine rpms are above 2000.
That is the job of the oil pressure circuit board. The circuit board
watches the engine rpm and when the rpm goes above 2000 it allows the
higher pressure switch to control the oil warning light. When the rpms
drop below 2000, it connects only the low pressure switch to the warning
light.

Mark

Matthew C. Huntley wrote:

>What is a "oil pressure differential circuit board" used for?
>Why is it there?
>
>Matt
>
>