DOMETIC AC SWITCHING BACK AND FORTH BETWEEN HEAT AND AIR

Most penguin model have the board in the upper unit on the curb side under a panel. I assume you have a heat pump and it is switching between heat and cool? Older models energized the solenoid in the cool mode,. new model energize it in heat mode. So an older model will switch if the coil is bad or intermittent, or there is a bad connection.
There are a bunch of control setups on these- 4 button CCC, 5 Button, 10 button, Analog, Single Zone LCD, etc.