More info is needed...
Are you saying you are getting water at a sink when you turn on the hot water, but it just is not hot? Or are you saying you get no flow from a tap when you turn on the hot water?
Your question sort of implies that the hot water has worked properly since buying this (new to you) unit at other times, like when using the fresh water tank. If not, have you checked to see if there is water in your hot water heater?
2013 Windjammer 3008W
2006 Chevy Silverado 2500HD 6.0L w/Equalizer 4
Nights camped: 2012 (29); 2013 (26); 2014 (40); 2015 (43); 2016 (35)