Heat help!

The back heat on my 95 AWD aerostar blows out cold air. The front(dash) is blowing out hot air like normal. Is there a door in the air duct somewhere between the front and back that could be stuck open? And where might it be located.
Thanks,
Teddy

sounds like your low on antifreeze. did you check it
mine was doing same thing just added some fluid and it was all good, ;)