My home garage door has been without a working opener since we purchased our house a while back. we bought and installed a 1/2HP chain drive unit from Sears, and hooked everything up correctly. the door is a large 2-car garage single opening (I think it's between 12-16 ft) segmented door with a dual track system( the top segment's upper guide wheels ride on a separate track than the rest of the guide wheels) and it works just fine on the way up...the problem is, when you press the button to close the door again, the unit pushes the door to about 3/4 closed, and then instead of closing the top segment, begins pushing down on the door itself, bending the top segment and the chain drive assembly. I know that the opener needs to continue pushing straight forward rather than beginning to apply downward pressure to close the door, I just can't figure out how to accomplish that. I've had this problem for 6 months now, and I can't figure out how to fix, although I'm sure it can be done, as there was a working garage door opener installed when the previous owners lived here