I'm having trouble with the fans on the rad of my 2wd Saph Cossie, I've changed the sensor in the rad and checked all the fuses but they won't come on when the engine gets hot. My dads removed the cover from the engine management relay in the main fuse box and operated this manually and the fans come on!!! I've tried another relay but they still won't come on by themselves.

Has anyone else had this problem and how to fix it!!!!