Thermal overload which means it's overheating. My PD unit has three 25 amp fuses on it. The power to the fan runs thorough one of the fuses. I'm not saying the fan is the only thing that runs through the fuse but certainly the fan is one of the things that does.
The converter may be difficult to get to depending how the unit was designed. Mine is a Jayco and Jayco for some stupid reason located the converter behind the panel in my basement storage area. I have to remove about 10 screws and pull the panel down to get to the converter. Some time this winter I plan to cut an access door into the panel so I don't have to remove the entire panel.
