We have a 1990 Holiday Rambler and while camping a month ago we shut off the generator because of low fuel and we did realize that during the night the steps were making a clicking noise. The engine battery had to be jumped for us to leave and everything seemed to be working ok. We parked the unit and when we tried to start it 2 wks later the battery was dead so we bought a new battery. We went on the road, generator ran and refrig & ac was good.  We stayed 4 days camping with electrical hookup and unit started up just fine to leave. We had a flat and had to wait so we turned off the unit, ran the generator and used our 4 ways. About 5 hrs later the 4 ways stopped but genertor was still running. We got back on the road and about 100 miles later the battery voltage on the new engine battery dropped down to 9 but we made it another 30 miles to home. The next day the unit started up but the voltage is still @ 9. Could this be our alternator?

If you drove 30 miles and the battery didn't improve from 9 volts I'd say you definitely have some kind of charging problem.  When the alternator is charging properly you should get a reading of 13+ volts when the engine is running, either on your dash volt gauge or using a test meter on the battery.  You've already replaced the battery so it sounds like the battery isn't getting charged as needed.  On an older coach it's also important to check all chassis grounds for corrosion along with all battery connections.