Is there any pressure regulator on Audi A-80, 2.0 engine model 1990?

SOURCE: Audi 80 oil pressure light

i think from memory that the oil pressure switch is at the back of the cylinder head, if its not there it will be located just above the oil filter, these switches are very cheep to buy and can be bought from any good motor factors. You are right to suspect the switch, its the first thing to eliminate before bogging your self down with more complicated and expensive problems.