Hi Boris,

I don't have the correct manual here, and asked you for the link to get it.

Look at the last few pages of the manual for the pages that tell you what the
schematic items are.

You should locate the low beam pages for your car to understand what happens to
run the low beams. There will be a 12V line from the main light switch to the lamp controller and output from the controller to the low beams.
The Volvo schematic give you the relay/controller socket pin numbers AND the
harness connector pin numbers to aid testing with your VOM. Note the Bulb out sensor is in series with the low beams.

If you have a junk yard near you you can get a light switch and controller cheap.
If you go to the dealer bring a fat bankroll and take a strong sedative before you hear the price.

Cheers, Bill