This is a great thread. Regarding the humidity heater on the Dometic 2652 etc... and the thread referencing it, this is a significant problem for boondocking. No switch to turn it off. I pulled the cover off the back of the refrigerator today to take a look at what i could do besides cutting the wire at the inside of the frig at the light. As mentioned, Dometic saw fit not to provide a switch to turn off the 12 volt heater off on the newer models.
I think an easy fix for now that won't void the warranty is simply pull the plug J2 from the printed circuit board. The only problem is the light in the frig won't work either since J2 feeds both the heater and the light. I think I'm going to put an external switch on J2 so I can turn it on an off without pulling the cover off the module.
See the attached picture. J2 is the first wire (red) on the printed circuit board at the bottom left. Any other solutions appreciated.