On the side of the motor unit you will find the 'up and down limit' controls. Using a small screwdriver turn the 'down limit' a couple turns in the opposite direction of the arrow printed on the cover. You will probably have to tweak this to get it just right. Remember when tweaking if you run the door too much the thermal switch on the motor will turn it off and you will have to wait about 15 minutes for it to cool. This is a normal.