Water bay Heat on Mandalay

Thanks for the help. I have seen my bay temp from 88-48 with ambient of 17-35. But my furnaces warm the bay also.

On my HR, my bay heat switch has to be turned on, then it goes to a disk, if the disk drops below 40 then the heat turns on...I found the disk an sprayed dust cleaner on it which is very cold and SNAP, the heat turned on...I'd call Thor customer support and ask if they used a disc or other thermostatic device and where that's located.

The 12 volt Cargo heater on Mandalay's is the same one Monaco used. There is a snap disc Tstat mounted on the inside area of the water bay panel. When you turn the switch ON, that activates power to that tstst. When the temp of the compartment drops below 34 degrees, the snap disc closes and the heater turns on. Follow the wiring from the heater and you will see that snap disc(1 inch in diameter). You can test with a PC spray air can held upside down. Monaco systems had a red LED at the inside panel by the ON/OFF switch that came ON when the snap disc was closed and the heater was running. Doug

It might help to know the model year.

It only operates when the temp inside the compartment drops to a preset temp which I can not remember. I owned a 2005 40D Mandalay a few years ago.

Do you also have heat on in the coach . Don't know about your coach but some (many or all) don't have separate heat source. It may be a switch for a fan that turns on and supplies heat when coach heat is operating.