Joanne,
I read through your posts and it's not clear to me if you're needing troubleshooting help, or just asking about the System Heat in general. With the power switch on, the heater in the wet bay will activate when the temperature inside the bay gets near freezing. Much like a furnace in a house, it will run until the thermostat shuts the system off.
Look in your wet bay for the heater. Previous posts have photos of what to look for and note that it may be tucked behind stuff. You might also have the heating pads. These look the same as a heating pad you'd buy at Walgreens.
The heaters sometimes fail and owners/technicians don't always repair things back to factory specifications so some of what we're describing might not look the same as what you find. I know this first hand.
Close up photos of your wet bay will help us help help you. 🙂
Jerry