it can be the floor board in the duct. however if you replace a board , if memory serves me, you have to perform a lon download for the controller to see the new board. i believe 5-7-1 is the menu. you chage it from 0 to 1 and it starts the sequence and runs it . when the menu goes back to 5-7-1 its done. best you get a manual explaining, i am going from a 3 year old memory here.