Whenever I read a statement " I checked the 50amp slow blow fuse and it appears ok. " I wonder why the word "appears" belongs in the sentence. After all, a fuse is either good or bad, and there is no in-between, so this leaves me with the assumption that you visually checked the fuse, and you didn't see any discernable indication of a defect with the fuse. If this is the case, then you need to recheck the fuse properly, and that is with an ohm meter. Fuses can appear to be functional when looking for a break in the filament and not seeing one, however, they still can be defective. You can't see the entire fuse filament at the metal ends or the attachment of the filament to the spades under a plastic fuse. If you don't have a meter to check the fuse, then replace the fuse to see if the situation changes. If there is a short in the wiring, then the new fuse is going to also fail, so this is really not a reliable method of testing that I rarely would recommend.