4x4 cossie radiator fans run from a black 40A relay in the fusebox - roughly in the centre of the fusebox slightly towards the front where the 2 rows of fuses are. the wiring to this relay has a habit of melting around the fusebox area.

the interior blower is not connected with the radiator fans in any way.

has your car been sitting for a while? there is a 3 stage resistor for the interior blower mounted in the centre of the blower assembly. this could've corroded, as could the conections to it and the earth. take off the black air inlet that is between the bonnet and windscreen, and unbolt the bulkhead panel in front of the blower motor and check it all out.