Did you actually pull the fuses out and check them with a VOM meter? They may "look" OK, but in actuality they are burned open or have a high resistance which in either case they need to be replaced. Electrical problems are difficult to trace and checking for voltage and continuity are the only way to find the problem(s).
Since you are having the same problem with 2 different circuits, my guess is that you are going to find the problem in the fuse block. If it were only in one circuit then I would say you would have to chase it from the fuse block through the switches to the fan.
If you do not have a VOM meter and do not want to purchase one, just change both fuses and see what happens, it is a cheap and easy test to see if that fixes it or if you need to chase it further, or pay a chassis mechanic to chase it down for you. An RV dealer will not be bothered to do this and will refuse to work on it.
Berniece & Russell with LilBit a Netherland Dwarf rabbit
1987 Southwind, 1995 Ford F150 Supercab 4X4 toad
Life in the fast lane? No thanks! We will stop and smell the flowers at every chance.