A 'thinky?' From a Marine? Hmmm.

Anyway, here's 2 cents worth. In a camper, you have two types of heat from your A/C units: Heat sticks (very rare in a Prevert conversion) and heat pumps.

Heat pumps actually run the A/C units 'backwards,' and are designed to do just that. If you have a cruise air with SMX, you can go to the front of the POG site and download or look at the SMX control manual for heat pump operation. If you have roof airs, usually there is a setting on the thermostat which will invoke the heat exchanger.

Depending upon your altitute and ambient air temperature/humidity, a heat pump is good to go at between 28-35F, assuming a fully-charged and in good condition unit (clean those A/C filters troops).

Air conditioners with heat pumps like to blow hot air. Wait a minute....ah....anyway, you get it.

The alternative to using heat pumps is, well, y'know.