Pat, there are two snap disks in that compartment. The one that is dangling, I have the same situation, does not control the ceramic heater. The one controlling the ceramic heater is on the floor of the compartment just to the outboard side of the winterizing pump. Look right up against the front wall of the compartment.
I don't know what the other snap disk controls. On our rig, and I assume yours as well, has a heating coil from the Aquahot system in the compartment. I don't know what turns it on but I assume it comes on with either zone 2 or 3 heat.
I have a remote temp sensor I put in the service bay and at times I see the temp get as high as 70 deg before the ceramic heater shuts off. Don't like that but with the snap disk on the floor I can see why that happens.
If you figure out what the hanging snap disk is let me know - I haven't figured it out.
For info I had to replace the thermal fuse in the ceramic heater last year. I can give you the details via email if you like.
2016 Winnebago Cambria 30J