what is the name of the vent that stops the heat from coming in when the ac is on?

A car's air system works in only a couple of ways. Air Conditioners work by filtering and drawing air in from the outside and then running it through a system of tubes and hoses that cool the air before running it out of the vents inside your car. Heat is generated similarly, except that it draws in filtered air from outside and then runs the air over a heating coil (regulated by the engines cooling system...the radiator, coolant, etc.) before pumping it into your car. Alternatively, both systems can also recirculate the air inside the car, rather than draw the air in from outside. If you have heat coming through your vents with the AC on, you probably need your AC recharged or your AC needs to be serviced. Heated air from the engine shouldn't enter the vents or be felt inside the car, since the climate control system only draws air from outside the car or from inside the cabin.

I have a 2004 BMW 645Ci crank no start situation took it to BMW they suggested a diagnostic test i had them run the test they said it needed the SGM module my question is will that cause it not to start

Heat is coming through the vents with my AC on but the car has been sitting up with a dead battery for years but was working before so now that’s what’s going on so is there a way to reset it