When I connect fan motor fuse blows immediately

Hello,

This happens because you have a short to ground in the fan circuit. I don't have access to Opel wiring diagrams but if you trace the wires from the connector on the fan back you will find it. This happens because of Ohm's law. If you have one of the three electrical properties that is constant(Voltage), then if one of the others go down(Resistance/bare wire touching a ground path back to Battery negative resistance goes to zero) the last one must go up(Amperage goes up proportionally/ Resistance to zero=Amperage to infinity). As the Amperage surpasses the rating of the fuse, pop, it blows, protecting the circuit, just like it's supposed to. Find the short to ground and repair. Please get back to us with how everything turns out.

Thanks,
Alex
2CarPros