Mine do not have electric tank heaters and have heat ducts from the furnace that heat the water lines and holding tanks. I'm assuming that's what you have also unless someone added aftermarket electric heaters.
Our 1997 GS has a furnace duct running down into the middle space where all the fresh water and holding tanks are located. Nothing else needed. Just run the furnace. If you do not feel heat near the fresh water tank, check the ducts inside the motorhome. Mice got in our tank space and chewed up the flexible metal heating pipe used by the factory to send heat into the space. The mice then crawled up the pipe and chewed out by the furnace to gain access to the interior space. Took lots of detective work to find the problem and replace the metal pipe that is similar to clothes dryer vent hose.
Originally Posted by Rugoin7777
Does anyone know Where the switch is to turn on the holding tank heaters on a 1999 28 ft gulfstream palm breeze RV Motorhome?..