Just a short recap on this. Many thanks Wotname for suggestions on how to test the shunt and meter. I tested the meter with 1,5v battery
connected on the signal wire and got some other readings other that -155. So the meter works.
I hooked multimeter for the signal pin on the shunt, got nothing. Took a picture about the measurements and send them to my dealer. They advised to bring the whole device there and few days later I got a replacement. Hooked that up on the boat and it works like a charm. Gives me readings while loading and charging
Thanks for help and suggestions everyone.