SOLVED! 
I have discovered that suddenly I've lost all the left side turn lights. After checking fuses, harnesses and connectors it seems that the Flasher Control Module was the culprit.
Because I was going to have next day a long trip and it seems impossible to get in time a replacement for the Flasher Control Module, I have decided to dismantle it, trying to find a temporary solution to have at least some turn lights working.
Inside it I've found a classic schematic with a small IC controller and two RELAYS, one for each side.
Looking at the solder side I've discovered that the solder around one of the pins of the left side relay was cracked, making no contact anymore to the board. Looking carefully, I've found that all the pins of both relays have different stages of cracks around them.
I believe that this appeared in time, due to the vibration of the inner armature of the relay, transmitted to the pins.
I have resoldered all the relay's pins, and it is working like new.
I have attached an image with the board, the cracked solder being quite visible.
I have discovered that suddenly I've lost all the left side turn lights. After checking fuses, harnesses and connectors it seems that the Flasher Control Module was the culprit.
Because I was going to have next day a long trip and it seems impossible to get in time a replacement for the Flasher Control Module, I have decided to dismantle it, trying to find a temporary solution to have at least some turn lights working.
Inside it I've found a classic schematic with a small IC controller and two RELAYS, one for each side.
Looking at the solder side I've discovered that the solder around one of the pins of the left side relay was cracked, making no contact anymore to the board. Looking carefully, I've found that all the pins of both relays have different stages of cracks around them.
I believe that this appeared in time, due to the vibration of the inner armature of the relay, transmitted to the pins.
I have resoldered all the relay's pins, and it is working like new.
I have attached an image with the board, the cracked solder being quite visible.
