Dreaded 0il pressure light and 3 beeps on 1.8 A4 1998 non turbo in the UK.

[500comet]

My oil pressure light kept coming on when the engine was hot and revs below 1800.
The problem is normally found on turbos where the oil has been carbonised by the hot turbo and blocks the gause filter in the sump. My car has no turbo and is petrol powered and the oil has been changed regularly for the last 10 years, so doubted this was my problem.
There were no rattles from the cam followers or cam chain so concluded that oil pressure was OK.
Have changed the oil sensor switch and all is now OK.

Others have said that changing the switch was easy. It came out OK with a long socket spanner but it was very difficult to put the new one in because it was impossible to see the hole to screw it into and get the angles correct to start the thread.
Had to make an extension to plug onto the electrical tag on the switch to enable me to feed it in and also to plug a long 8mm rod in the form of a drill into the threaded hole first so that it stuck out to enable me to have an idea of the angles involved.
The job was not easy by any means, and resulted in some badly damaged knuckles, but perhaps the layout is different with better access for the Turbo models.
I think I was lucky to have fixed my problem without cleaning out the sump (oil pan).

By he way I suspect the oil pumps very rarely fail, but the problem is the oil pressure relief valve in a pump which may stick open and can be replaced/cleaned.

Matty

[a4kamila6]

Some pictures would be nice but regardless good job on figuring it out on your own.

[500comet]

Pictures would have been difficult to take because my hands were well occupied trying to get the sensor thread aligned and in any case would have been covered in blood from my damaged knuckles.
I spent over three hours trying to get the thread to bite - then walked away to make a phone call, came back, picked up the sensor and it went straight in - just pure luck !!

[500comet]

I forgot to say by the way that my 1998 1800 A4 has done 170,000 miles and runs beautifully except for a short rattle on start up which it has had for some years.
The cam chain tensioner has been changed for a simple one with no VVT electrical connection but this did not fix the rattle. This was much cheaper than the proper tensioner and removing the VVT circuit made no noticeable difference to performance except that the fuel consumption is better by around 10% at 36mpg (imperial) running around and 40+ mpg on a run. !!!

[4A Play]

I drained my oil, poured a gallon of kero in my valve cover, let it sit overnight, drained it. New oil. Pulled the valve cover and air compressed it up. No more oil pressure warning light.