We purchased a 2015 Savannah in June, 2014. After 3 months the converter began a high-pitched hum, and the dealer replaced from a Savannah on the lot. After several months this converter also began to hum...but not constantly. Has anyone had problems with the converter? What does the hum mean? We are full-time RVers, and I would prefer to not wait until the converter fails. Thanks for your input.