Heater core or not heater core? That is the question.

So I have a 1955 chevy 210 and once in a while when I drive it I smell antifreeze and the passenger side window fogs up a little bit. I've read and read and read online and everything I read says u will smell antifreeze and see fog when the heater is on. Well mine does it when the heater is off. So my question I ha e before I spend a ton of money on parts is this. Is it my heater core still if it's doing it when the heater is off? Any help will be so greatly appreciated. Thanks in advance.