Author Topic: oil pressure sending units and wiring (Read 3955 times)

tdi4by · « **on:** August 11, 2007, 04:17:10 pm »

Why are there 2 sending units? one on the side of the head and one on the oil filter adapter? Are they supposed to be different? mine has two Black ones and the one on the oil filter adapter has a yellow wire and the one on the side of the head has a blue wire. I tried grounding the wires to see what lights come on and the blue wire makes the oil light flash and the yellow one didn't do anything?? I am installing an oil pressure guage and I am wondering wich one I can get rid of.

Vincent Waldon · « **Reply #1 on:** August 11, 2007, 07:07:40 pm »

It's a fairly sophisticated system with two pressure sensors... one that trips at 0.3 bar and one at 1.8bar (IIRC). One is normally grounded and the other is normally open... electronics in the dash cluster decide which sensor to pay attention to based on engine RPM... the low pressure one below 2000 RPM and the high pressure one above 2000 RPM.

The Bentley service manual has the complete troubleshooting guide, but if you search for "dynamic oil pressure" or thereabouts on this board you will find tons and tons and tons of discussion... comes up every 2 weeks or so like clockwork.

Vince

tdi4by · « **Reply #2 on:** August 11, 2007, 10:36:11 pm »

Thank you, I guess that is why my old 89 GLI flashed the oil light at times but would quit when I reved it past 2 grand or something. I can't remember exactly but I just learned to live with it.

Vincent Waldon · « **Reply #3 on:** August 11, 2007, 11:15:30 pm »

Quote from: "tdi4by"

Thank you, I guess that is why my old 89 GLI flashed the oil light at times but would quit when I reved it past 2 grand or something. I can't remember exactly but I just learned to live with it.

That's *exactly* it... another VW mystery solved for ya !!

Vince