Hello Rob and Edna and

. We are glad to have you join us here and we look forward to reading of your adventures and experiences. I am sure you will enjoy the website and forums. Good luck, stay safe and keep us posted.
Take all of the light bulbs that are on the circuit out of their fixtures and retry the fuse. I have had light bulbs be shorted internally. If the fuse does not blow (turn on all switches) then re-install the bulbs one at a time. When the fuse blows, there is the culprit.
If the fuse still blow with all the light bulbs out you will have to also remove the fan from the circuit. Are you experienced with electricity and 12 volt DC circuitry? If so let us know and we can help you diagnose the problem
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Mike, Certified Master RV Technician
Amy, RV Merchandiser; Roxie & Mei Ling, four legs each
2000 Gulf Stream Scenic Cruiser w/ Banks & 2 toads