I recently replaced my oil psi sending unit on my '92 400E. Seemed to work great. Now, I have a strange problem.

When I turn the key to "on" position, the guage immediately jumps to "3". When the car is a running temp and I am at idle or slowing down to idle, the guage measures oil psi properly. As soon as I come to a complete stop with brake applied, the guage jumps to "3". Upon release of brake and slight excelleration, the guage drops sightly and begins to read psi.

If I am at idle and the car is in "P", the guage works fine.

Is there a voltage problem or short somewhere?

I installed an OEM sending unit (FYI)...wiring at the unit was quite simple. I can't imagine that I screwed that up.

Comments and advice is appreciated

Loose connector or slight break in wiring. Open circuit will cause the gauge to read 3bar.

Can be the oil psi sending unit as well..
I have replaced the sender on my 190D by a new MB sender once. After about 3 months and a trip of 100km flat out my gauge went down to 0 while I stood in front of a traffic light (can you imagine the look on my face...).
I turned down the window to hear the engine, but it still sounded like the oil pressure was good.

It took me a new oil-pump and oil-filter housing before I found out that the sending unit was BAD. Normally when the sender is broken or the cable is disconnected (partly or total) the gauge will go directly to 3 when the ignition key is turned on.

greetingz,

It jumps to 3 upon ignition "on" position. Then, when the engine cranks, it drops toward 0 and immediately returns to 3 with oil psi.

It's quite interesting to watch the guage at operating temp at a stop light. With Brake applied, it quivers at 3. As soon as I release the brake and begin a slow accel, the gauge drops to 1 and begins it accent to 3 with psi...

I am gonna re-check my wiring connection at the sending unit this weekend.

Can anyone give me a tip as to where the wire terminates on the other side?

Thanks