Coolant / Refrigerant

[Russell Marlowe]

Ok, so for the life of me, I can't figure this out on our new to us M380.

On the back of the coach, there is what looks like a fuel filler door with what looks like a radiator cap behind it located above the engine where you would expect a radiator fill to be.

But when I open the engine compartment, immediately below that door/cap is a big tank with a "Cold fill" indicator and some caution notices about refrigerant.

Is the door & cap where I put in antifreeze/coolant and the labels are for something else? It just doesn't make sense to me, and I sure don't want to pour coolant into something else!

Thanks!

Russ Marlowe