I do have a multimeter and a flashing lamp. 3 times, and red + beep.

I understand that means low (or no) pressure warning.

How can I check the oil pressure switch?

 

My car is 2000 model Fabia (6Y2) 1.4mpi.

Can "relief valve failure" be the problem on this one as well?

I do have a multimeter and a flashing lamp. 3 times, and red + beep.

I understand that means low (or no) pressure warning.

How can I check the oil pressure switch?

 

My car is 2000 model Fabia (6Y2) 1.4mpi.

Can "relief valve failure" be the problem on this one as well?

Check it visually, looking for oil coming out of it around the plastic areas (disconnect the wiring connector first to see better).

Some pictures of location and how to change it if necessary in this thread.

Common for the switches to fail on this engine, relief valve failure unlikely, and would tend to give higher pressure, not lower, I think.

Thread moved from Classics section.