I have a portable AC unit connected to a window. Will running my furnace fan help circulate the cold air? Or is it pulling in hot air outside?
I have used the furnace to circulate even swamp cooler air not really cold but cooler and it made the home a bit more comfortable.
If you have a make up air intake damper close it almost all the way down you only need a tiny amount of make up air when the fan is on full time.
Yes your single hose is pushing really hot air out but some air will be drawn in to the home one short term suggestion I make to homeowners is to slightly open the access to your crawl space. Opening the crawl space pulls cooler air in from under the home as long as the air going out is hotter than the air coming in the home will be cooled.
Even air movement alone helps us to be cooler so the air handler running distributes the air evenly through the home and moving air also helps.
Some furnaces only circulate air and do not draw in fresh air. If you have one of those (only circulating) it may feel like it is pulling in hot air simply because the A/C is not capable of cooling your whole house in addition to the HVAC ducts themselves and through them the attic/basement/walls or wherever else they go. In fact, if the ductwork runs through the attic who knows, it may pull more heat in that way than is removed by the A/C! To improve your chances slightly you can make sure doors are open, or closed, to the rooms you want cooled or not cooled respectively, and don't forget to keep cleaning or replacing your furnace filters while you are running the fan even if you are not heating. You may find that just leaving interior doors open circulates the air well enough, and conserves more of the coolness for your living spaces.