Hi kc57,
Welcome to the Heartland Owners Forum and Family. We have a great bunch of people here with lots of information and all willing to share their knowledge if needed.
Not sure if your Jensen has other inputs, but you might check the remote control for a "scource" , "input" or some other button that will allow your radio to be switched so it is just an amplifier for another unit like the TV or a dvd player. It might be just waiting for some input from something else. Maybe someone with the same unit will jump in soon.
Enjoy the forum.
Jim M