Brother of The Benz, Bobco
To find where the short is in a stand of circuits, you go to the furtherist point of the wire.
Remove all of the bulbs and the fuse. Use your ohm/continuity meter and check the wires to ground. If all are ok replace the components and move on in the same manner to the electrical components,(blower motors, etc.) .
You will evidentually isolate the culpert.
Happy Trails Beep Beep from The Spiderman in Houston!!!