Ric,
I installed a 13.5k Carrier in the bedroom of my Landmark so I know a little (and I mean a little
) about the units. But I can tell you the plastic roof shroud has vents to the outside that will allow light in (as in under the main shroud but the internal unit is sealed from the outside). Under the shroud is another translucent plastic dome that is sealed but will allow sunlight to illuminate it from the inside.
Now, there is a foam gasket that seals the a/c unit to the roof. If light is coming in through the seal in the gasket, that is a big problem as your unit is not secured and could blow off. However, if you are only seeing the suns glow through the translucent plastic, it is nothng to worry about.
Like others have said, the unit is sealed from outside air so no heat should be leaving the coach through the a/c unit.
John