I would be surprised if a 95 Southwind has a water filter unless added aftermarket. It wasn't common back then and my 96 Southwind 36 footer do not have one from the factory.
The electric dump valve is also an aftermarket add-on. Try tracing the wiring and use a voltmeter to check for 12v at close as you can to the valve. That will tell you if it is a fuse or the valve itself.
Former owner of 2004 American Tradition and several other RVs
Home is West Palm Beach, FL