Hi 1 2 3 and 4 work when i put it on 5 it clicks so i was looking to see where the clicking came from under the dash near fan motor so i wiggled the wire a bit then it smoked a little so i felt the little black box it was warm so i wiggled ires again fan came on but the box is still warm so do i nead to replace that box and what is it called it looks like a set of wires from the switch go to it and from there to the fan its a 2005 silverado 4x4
Thanks Bill

 

It is the blower relay. Speeds 1,2,3,4 all run through the resistor but speed 5 is a straight shot of power. The relay is used to allow the circuit to deliver the extra amperage need to run the blower wide open.

 

Blower motor resistor.

 

Speed 5 does not go through the resistor