If the dealer who sold you the motorhome is an authorized repair facility for Onan, they can take care of it, and it should be done promptly and at no cost to you. If they are not an Onan repair facility, find a Cummins/Onan shop who will quickly fix or replace your unit. I went through the same thing a year ago, and Cummins had me back in business shortly. Overall, Onan generators are very dependable and trouble-free, but the fuel you get today deals much misery. That is the #1 problem they have with new Onans, according to the service tech I dealt with. Be sure and exercise your unit monthly as is recommended, too (after it gets fixed). Don't worry about putting too many hours on the generator, more hours are far better than few hours.
Mike