The previous owner told me the heater didn't work, but me being the fixit guy that I am, decided to investigate. I knew that it wouldn't work with the small battery charger they had wired in to power the 12v, but I had just replaced the converter with a new one. Referenced in his thread http://www.popupportal.com/index.php?topic=100374.0 I clicked on the thermostat and the fuse blew immediately. I assumed it was a shorted blower motor or something else internal to the heater. So I pulled it out and checked the wiring in the unit. No problem found. I replaced the fuse and, leaving the heater out, I tested voltage on the wires to the heater. I had 12v. So I turned on the thermostat and the voltage dropped to 0v. I then pulled out the thermostat and looked for problems there. Nothing. Next I pulled the refrigerator and lo and behold there it was. The thermostat wires were ran between the lift cables and one had wore through causing a short to ground. I repaired and rerouted the wires. Tested the voltage to heater again and all is good, so I reinstalled the heater and it works.