Blown fuse = resistance, short (or old age). It would blow immediately if you had a direct short to ground. You could pull out the volt meter and set it to amps then look for any excessive draw. I'd probably change the fuse making sure that it was the proper size and see if it blows again. A worthwhile project is make sure that the contacts in the fuse box are clean where they make contact with the fuses. Deoxit works well for cleaning contacts. You could go wild and clean every contact you can get to - it couldn't hurt. Some on my SD are nasty but it is cold outside.

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85SD 240K & stopped counting painted, putting bac together. 84SD 180,000. sold to a neighbor and member here but I forget his handle. The 84 is much improved from when I had it. 85TD beginning to repair to DD status. Lots of stuff to do.