I have a Bryant Plus 80 gas furnace. Everytime the unit shuts down there is a loud bang. I am not sure if it is a metal on metal sound but that may be what it is. Anyone know why this may happen? It is annoying and wakes up our baby at times (the furnace is in the hall across from the room). I am sure it is something that probably needs to be checked out by a pro but I thought I would ask anyway. Any help or direction would be greatly appreciated.