Fan for heat and air conditioning

This is mostly caused by corrosion on the terminals of the resistor pack, to access it you need to remove the vent just above the bonnet where your wiper and wiper motor is located, in the centre you will find a housing that houses your blower motor, remove the top cover of the housing and follow the path of the wires going into the housing which goes to a resistor pack and is held down by a screw, remove screw and resistor pack check connectors of resistor pack should be corroded and rusted, clean it off with sandpaper and lubricate contacts or replace unit, re-fitting is the reversal of removing.