Is the air exchange suppose to be open or closed when running window air conditioner?

Question

It is a very old GE model that does not have a filter just metal fins on the outside and also on the inside.

Answer 1

HVAC Tech.: If the air in That is a bit stale you can open the exchange and pull in some fresh air from outside. Of course, that means pulling in warm/moist air that will need to be cooled and dried. Most of the time you would want it closed to save$$$$$

Answer 2

Keep closed for maximum cooling.

When it's open your letting some fresh air in, and of coarse more heat and humidity in.

A filter should always be in front of the cooling coils.

They can be purchased at most hardware stores.