headlights turning on and off by themselves

[Gabriel Jimenez]

my 1992 lancia thema 16v ie has begun to act oddly. sometimes the headlights (street) do not turn on, and sometimes do when I turn the control lever. I checked the lamps but are ok, and the same with the fuses. I know that every mayor electrical item uses relays but I cant find the one for the headlamps. Position lights, higher (road) lights and turning lights work fine.
Greetings from Chile, Southamerica