If the fuse is blowing immediately then yes you have a short somewhere. Did you see any magic smoke when this happened? I have seen the wiring inside the harnesses melt and fuse together from such mishaps. You have already isolated it to that fused circuit so start disconnecting things on that circuit( clock/ radio / etc ) Will need wiring diagram I'm sure. If when all consumers are disconnected and the fuse still blows the wiring is shorted to ground. It is possible one of the components is shorted internally which is why I would suggest disconnecting them all first. You may have to start tracing wiring to find the melted / shorted area by pulling back the wiring loom/tape. What year is it? There are wiring diagrams available here on forum I believe but not all years.
Matt