Sounds like you went the wrong way with the down limit control. When the door hits the floor too hard the safety senses the door has hit something and reverses to the open position. Turn the down limit in the opposite direction of the arrow printed on the cover until the door stops short of the floor. Now you can adjust the control in the opposite direction until you have it right. If you run the door to much during this operation it may turn off if the motor gets hot. Let it sit for about 10 or 15 minutes and you can start again.

Thanks Don,

My garage closes now. I have tried both up and down limit before your advice, but did not do it in small increment and therefore did not work. With your advice I turned the up and down limit with small increment until it is just right, and it works. I did not know an opener can be so sensitive to its limit. Anyway thanks again for your advice.