If you are having problems heating and cooling your home and everything is working right with your central heating and air conditioning system, chances are the issue is with your windows! First off, you should never leave a window open while running a central heating and air conditioning system.
This totally defeats the reason for having heating or air conditioning in the first place.
Second off, a lot of times people do not know the window is opened because it may not have shut properly and could still be slightly cracked. Always double check this before turning on your central heating and air conditioning system. Also, you may want to check your weather stripping on the window. This could also be an issue and make your central heating and air conditioning system not work right in terms of air flow and heating or cooling your home. All of these things are a major thing. Not only that, but when there is outside air seeping in from the windows it also causes the central heating and air conditioning system to work overtime. And this could lead to the motor of your central heat and a/c unit burning itself out. So it is very important to always check those windows in your home and make sure they are completely closed off! I started doing this after I ended up almost killing my HVAC system as a result of a weather stripping issue with my living room windows. I have ever since been very aware of all of it.