hi there. I have an audi a3 1.6 SE petrol 55 plate. The fan comes on (at full speed,very loud) as soon as i start the car and only turns off when i turn off the ignition and start the car again immediately. The fan only turns off when the i ive driven the car for a minimum of 45mins. When the fan is on, the engine management light shows. The temp gage is always on zero and only starts working when the car has been turned off and then re started as i mentioned above. The car does not over heat. The fan basically comes on when the engine is cool and turns off when the engine has warmed up. So far i have had the thermostat checked and its fine and also the water pump and the air pressure switch. There is no gas in the ac rad, can this be the problem? I was told that i need to change the whole radiator fan but when i connected a similar one to the car the same problem occured. the fan came on immediately. please help