Every time I plug-in a new 20 amp fuse to my cigarette lighter outlet located in the fuse box in the cab it short out immediately any suggestions would be much appreciated

 

Um.... start looking for the fault? It could be anywhere in the circuit, but most likely at the outlet itself.

 

I used to have that same thing going on but the reason mine was doing it you might want to check to see if any wires are touching the frame they had a cut ABS sensor wiring it was shorting out to the frame and I was constantly having to replace my fuse