Yet another Fiat Idea problem, end of last year got a 2nd hand thermostat in car as heaters cold, now i only get warm air again for few mins (if i'm lucky) i've noticed that the temp gauge acting weird, can be sitting about half way which is normal then when i stop at lights it drops down then as soon as i give it some revs to go again it goes back to where it was ?? Could this be the thermostat again? Checked water level and it's ok.