how can i fix my renault clio 1.2 1997 radator fan?

hello!

i recently took my clio for a m.o.t and during the m.o.t the car over heated.

the mechanic said that the radator fan is not working..
so i took it home and tested it nothing happend it wasnt spinning.. i buy a new fan and got it to work but it only works when u spin it to get it going.
but now a few days later the fan has stopped working altogether.. so ive connected it by running 1 cable from the fan into the car connected to a switch and from the switch to the battery.. the other cable is from the fan and goes directly to earthed... ive got it working a couple of times but all those times ive had to spin it to get it going... any1 have any ideas it would help me so much
thanks
dave