Both front and rear light brake valve does not work. When I bridge the wires it lights up so it is definitely the light valves. I was told at my local Ducati dealer that they are discontinued.
What can I do ???

For the rear, any hydralic light switch in a M10x1.0 thread should work try your local auto supply. I seem to remember some one found the same switch on a BMW motorcycle. I'm sure Guzzi has one as well.
For the front it is availible from a few sources here in the states, Maybe some one else can tell you where to find it in your neck of the world.

you may try www.stein-dinse.com in Germany. they hold large stock of Ducati and Guzzi parts.
in the front lines there is this dividing block underneath the lower yoke, when I'm right there is a thread unused. when so, it has M10 x 1 as higgy stated.
I've also seen microswitches on the mastercilinder at the handle bar.

Bertus

Both switches i`ve got here. Don`t need them, because i have them twice.
40€ for both, plus shipment.

or try www.conrad.de and look for microswitches. there a vast array of swichtes on their site. I use them also for my car.

Bertus

You have enlightened me enough thanks, I will do a research in the local market and then if nothing comes up I will buy from abroad.