Hi,
First check that your fuse is not blown. Then check your fan is working by disconnecting the two connectors from the sensor and touching them together with the ignition lights on. If the fan is o.k. it will start to run. If the fuse and fan are both o.k. you are left with just the sensor (plug with two connectors usually on the radiator), change this. Keep fingers away from the fan when testing!!
Cheers now
Ken Chapman
May 2007