I have a 1998 31ft Holiday Rambler Alumalite 5th Wheel trailer. Occasionally, my interior lighting and the furnace fan, if it happens to be on, will surge, meaning that the lights will get brighter and the fan will speed up. All of the above are 12 volt powered, so I am wondering if my converter is beginning to fail. I have also monitored the voltage on my 12 volt panel when this happens. It rises from the normal 13.45 volts up to 16.8 volts. It will hold there for maybe 20 or 30 seconds and then drop back to 13.45. I should also add, that this happens when the shore cable is connected. I have new batteries on the trailer, with good connections. Does this sound like the converter? Are these things repairable or must I purchase a new one? If so, which is the most reasonable place to buy such a thing. Thank you. Any help would be appreciated. Dave.