1995, 90 Quattro - low oil pressure light/buzz at 2,100 rpms +
 

Recently in my audi any time i rev at 2,100 or above 2,100 the low oil pressure light comes on. Unfortunately for me, my oil pressure gauge is not functioning. However i do think its still has decent pressure but i will need to test it for that. Where is the port to test for the oil presusre? Also just in-case its the sensor(s) where is the oil pressure sensor(s) (high rpm sensor?) the light comes on and the buzzing repeats three times, if i go under 2,100 rpms the light disappears.

Heres a video i found on Youtbube. We have the same exact problem.

https://cimg0.ibsrv.net/gimg/www.aud...d6708ccb80.gif

You have two oil pressure switches. One is a simple OP switch, probably on the backside of the block above the oil filter/cooler. The other should be incorporated into the oil pressure "can" which has two wires..one goes to your oil pressure gauge..the other to the dynamic oil pressure warning system.

The simple oil pressure switch is grounded when the OP is low and opens when the engine is running. The switch in the "can" is an open circuit till about .9 BAR, then it grounds the circuit when the OP reaches about .9 BAR

If the wires(s) on the OP "can" are loose or disconnected..then you will get the warning from the dynamic OP warning system above 2000 rpm..that is what the dynamic oil pressure warning system is looking for. The low pressure switch open circuit, engine running at idle and the high pressure switch circuit grounded to earth above 2000 RPM.

Could be a loose/broken wire on the "can" or a defective OP sender "can"

Or you may only have two simple oil pressure switches..they are different in how they operate. The "high pressure" switch could be defective or disconnected.


https://cimg2.ibsrv.net/gimg/www.aud...f3bd6a2206.jpg

Thank you for the information Rusty. The pictures help tremendously
I'm going to to be trying to get underneath the car this week. I had a camping trip over the weekend and didn't have the time to do it till i got back.

Is there a possibly you could show some more pictures of the location of both? I'm just un-sure where the "can" is, does the vehicle have a "catch can"? I've the term before but usually with turbo or high performance cars. Is it fairly easy to get to? i'm just trying to imagine how i would access it.
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Update:
Atleast for the knowledge of component location 12v.org had a awesome picture.


https://cimg7.ibsrv.net/gimg/www.aud...7e70ddef82.gif

https://cimg3.ibsrv.net/gimg/www.aud...c854ddc883.jpg

If you have the AAH 12v 2.8 engine..your oil pressure switch and silver oil pressure sender (can) will look like the picture above. Your car may or may not have this engine..it could be an AFC 12v 2.8. In which case the oil pressure sender and switch will inserted into the engine case itself..rather than an adapter made of brass as above.

In the picture below you can see the switch. This engine doesn't have the oil pressure sender for a gauge (can) like the AAH engine picture. There should be two senders, one on each side (I think) See what you got there.

If you have the big silver can (sender) it will be on the opposite side from the oil pressure switch in the picture below.


https://cimg3.ibsrv.net/gimg/www.aud...3432ba978e.jpg

Thank you for the photos Rusty, those are fantastic!

I'm going to be getting this done in the next day or so, ill post the results/new findings. Also going to try to clean out the bay and detect some new leaks. She's leaking badly.

What would be the easiest method to remove it? AFC motor. I was going to remove the oil boss but it Semmes attached to the pan?

https://cimg9.ibsrv.net/gimg/www.aud...e450fadc6e.jpg

On a AFC engine it is on the front side..just threads into the upper oil pan..see the pic. A 24mm deep socket can help.

So i replaced my AFC oil pressure switch with what autozone told me was a cross reference part. i called audi and asked for the part number, it was that or wait for shipping from a warehouse. part number # 028919081h i revived a oil switch for 2.2 bars. i dont think this is the right one, it fit into place (thread wise)but i still get the light. as-well as the oil switch (old one) was leaking oil around the rubber portion. do you know what oil switch to use on the 12v AFC 1995 Quattro? I called the stealership later after i got the same error just to double check i got the right reference number by them and then they told me part #078-919-081-C and well that one i think is correct i looked it up and is a switch rated for 2.5 bars? compared to the switch i was handed at autozone that was rated for 2.2 Bars

after examining the part and website for autzone i think they person gave me the SFL engine? Duralast make for switch.

Thank you!

On a better note, i have no more leaks i believe! :D

028919081H is a .25bar (3.6psi) low speed oil pressure switch that opens the electrical circuit when the oil pressure is at .25 bar.

078919081C is a 2.5bar (36psi) high speed oil pressure switch that closes the electrical circuit when the oil pressure hits 2.5 bar.

If you use the low speed switch when it should have a high speed switch the warning system thinks you don't have oil pressure..the switches work differently and cause false warnings.

You need a 078919081C (2.5bar) or if you can get one quickly a 068919081D (1.4bar) high speed oil pressure switch.

part number # 028919081h is the wrong switch

Thank you so much for the information. I called Audi and asked them to ship me an oil switch. Should be here this week hopefully when I put it in the light will be gone for good.