I don't know what brand converter you have. My 2005 had an IOTA unit. A friend's 2002 had one integrated in the power/fuse panel. Neither of them (and I am willing to bet yours too) had a "Smart Charger" capability. This likely caused your batteries to boil out most of their water, resulting in the battery going dead, and consequently had the charger working overtime (hence the fan) to try and charge the battery.
You are smart to upgrade your converter to one with a "Smart Charger" technology. There usually is sufficient space available to place the new converter. Move the battery charge cables from the old converter to the new one, and plug in the new converter to complete the conversion. Usually an easy job.
New RVs come with 90 amp converter. Depending on how many batteries you have and how much you boondock, 90 amps may be overkill. A 55 amp unit is probably sufficient for normal use.
Carl (n Susan)
There is more to life than fuel mileage.
2012 Montana 3700RL Big Sky Package towed by a 2015 Ford F350 6.7L PSD 4WD CC LWB