2004 Nissan Micra temperature gauge cold

Check/ replace thermostat. Check coolant level first .

Thanks, will do. I'll tell you a bit more history about the car.

I had a problem last year when the blowers started blowing cold. There was hardly any coolant in the system. Mechanic couldn't find any leaks, the water pump was ok and he put a cooler thermostat on (can't remember why) Refilling it took him ages as he said there were no bleed valves. Had a few problems with air locks and had to keep topping up. I've checked the water levels regularly over the past year and it only occasionally needs a slight top up. It has been running fine since January.

Would this new problem be related to that?

You could try bleeding the cooling system first but if thermostat is stuck open ,engine will run cool .If losing coolant a pressure test on system will show up any external leaks .

I still have a problem with this. I took the car to the garage where the mechanic sprayed the sensor with something (can't remember what)which cured the problem but only temporarily. I continued to use the car for a month or two before getting the sensor replaced. However, on almost completing a 14 mile journey straight after the new sensor was fitted, the blue light came on again. I drove straight to the garage where the mechanic checked the car again and thought it seemed very cool considering the length of journey I had done. What does this suggest? The car has a cooler thermometer fitted. Could this be a reason for the problem? Apart from the blue warning light being on, the car seems to be running ok.