(G) problems with my first uno!

Hi
i am new to this forum new to driving and new to fiats and my uno has developed something wrong with it the car seems to cut out everynow and then and the temp gauge shoots up so does the rev counter and when the engine does this nothing works i.e the hazards and the ignition light stays on it does start up again after a short while though my dad noticed that when you turned the air con off it started up again but it cut out shortley afterwards

the car is a uno 70 ie sx 1991 j

my dad thinks it could be an a bad earth i havent really got a clue but im goin away tomora so i aint gna be driving me uno till wen im bak