gdiilk

Hello everyone
I have an Audi 80, Cabriolet 1994 2.8-liter engine.
When I start up the engine oil pressure light of. When I get to 2000 rpm or higher, oil pressure light comes on.
Even when I hang up the Unit, oil pressure (both). Bulb comes on over 2000 rpm.
Someone familiar with the phenomenon, how can we solve this problem.
Oil pressure right in all situations. I checked with the oil pressure gage.


Excuse me if my English is not so good.

Rusty Spokes

Do you have an oil pressure gauge in the center console?

I ask as there is a low speed pressure oil switch and a high speed switch.

Your high speed oil pressure switch wire is disconnected or the switch has failed. I don't remember if the high speed switch is in the oil pressure sending unit or is separate. It should be a white/gray wire down above the oil filter.

It may look like this on the AAH engine..same place with a different mounting on the other side of a AFC engine:


The part number should be 078919081C..a 2.5 bar high speed oil pressure switch.

gdiilk

Hand 2 Unit near oil filter.
I'll check the wires today, but even when they are disconnected, this phenomenon repeats.
Oil pressure light bulb lit over 2000 rpm
Could it be that the problem in mini check system control module?

Rusty Spokes

If the wire to the high speed oil pressure switch is disconnected..then the warning will sound..the system looks for a ground above 2000rpm..that oil pressure switch works differently than most..it grounds the circuit at 2.5 bar

gdiilk

Thanks for the explanation
At end of week I'll check the wiring, and will update here

gdiilk

good morning
Today I checked the connections on the Unit according to the picture.
I have one white Unit (front) and one blue Unit (rear)
Everything looked fine.
Is it possible there is a problem on the dashboard?
Has anyone encountered a problem on the dashboard?

Rusty Spokes

I think your problem is one of the oil pressure switches or the wires are crossed and connected to the wrong switch OR you have defective oil pressure switch..probably the high speed switch.

Audi uses the dynamic oil pressure warning system..it is the same for many VW/Audi cars. The system uses two oil pressure switches. One is a "high speed" switch..usually about 2.5 bar..that creates a ground circuit (goes closed) when it has 2.5 bar of pressure.

The "low speed" oil pressure switch is "closed" and grounds the circuit until the oil pressure is about .3 bar..then it goes "open".

So both the switches work differently and opposite..and the dynamic oil system looks for the high speed switch to be grounded at about 2000 rpm to be sure you have 2.5 bar oil pressure.

The dynamic oil pressure system looks at the low speed switch below 2000 rpm to be sure you have .3 bar oil pressure by seeing an open circuit.

If the wires are crossed..you get a warning. If the high speed switch wire is not grounded above 2000 rpm you get a warning..if the low speed switch is grounded, you get a warning.

Almost always your problem is a disconnect wire/swapped wires or a defective high speed switch. Both switches are notorious for leaking oil too.

You should have a blue/black wire to the low speed .3 bar oil switch. And you should have a white/gray to the high speed oil pressure switch.

You may need a 078-919-081C (2.5bar) high speed oil pressure switch..the color may be red. It has the white gray wire. Or you can use a 1.4 bar 068-919-081D which may be brown or black in color.

The low speed switch may be blue or white. part number 028-919-081D It has the Blue/Black wire.