Crazy temperature needle fiat fold

Hi how are things?
I have a Fiat folded, I bought it from Secondamano and from the beginning it gave me problems with the temperature needle.
When traveling goes from maintaining the right temperature to fall by its own weight to 0. When it seems to recover.
I have not had overheating problem, it always remains well, the problem is that it falls continuously.
When I wear lights, there is a downturn in them when it falls.
I would appreciate your opinions and help.
Greetings and thanks for your time.

Can anyone help me?

Thank you

The only thing that occurs to me is that the needle "falls" because either this clock is left without food as to the signal it receives, or the cable that is bad of the sensor is poor (You are missing current.) Check it to see what you see. Greetings!!