Hi guys, Im new here, so please be patient with me

:P
I just bought a NX2000 and I have a couple of problems.
Ill begin with the fist one for now :P .
When I received the car, the fan was only working on 1,2 and three. So last week we changed the switch, now its working on 1,2,3 and 4. But when we put it on 4; the engine drops, the lights dim and you can hear the alternator working hard and then the fuses blow
So.. can anyone help me out ??
Thanks in advance,
Mat